diff --git a/CHANGELOG.md b/CHANGELOG.md new file mode 100644 --- /dev/null +++ b/CHANGELOG.md @@ -0,0 +1,5 @@ +# Revision history for webcolor-labels + +## 0.1.0.0 -- 2025-09-20 + +* First version. Released on an unsuspecting world. diff --git a/LICENSE b/LICENSE new file mode 100644 --- /dev/null +++ b/LICENSE @@ -0,0 +1,373 @@ +Mozilla Public License Version 2.0 +================================== + +1. Definitions +-------------- + +1.1. "Contributor" + means each individual or legal entity that creates, contributes to + the creation of, or owns Covered Software. + +1.2. "Contributor Version" + means the combination of the Contributions of others (if any) used + by a Contributor and that particular Contributor's Contribution. + +1.3. "Contribution" + means Covered Software of a particular Contributor. + +1.4. "Covered Software" + means Source Code Form to which the initial Contributor has attached + the notice in Exhibit A, the Executable Form of such Source Code + Form, and Modifications of such Source Code Form, in each case + including portions thereof. + +1.5. "Incompatible With Secondary Licenses" + means + + (a) that the initial Contributor has attached the notice described + in Exhibit B to the Covered Software; or + + (b) that the Covered Software was made available under the terms of + version 1.1 or earlier of the License, but not also under the + terms of a Secondary License. + +1.6. "Executable Form" + means any form of the work other than Source Code Form. + +1.7. "Larger Work" + means a work that combines Covered Software with other material, in + a separate file or files, that is not Covered Software. + +1.8. "License" + means this document. + +1.9. "Licensable" + means having the right to grant, to the maximum extent possible, + whether at the time of the initial grant or subsequently, any and + all of the rights conveyed by this License. + +1.10. "Modifications" + means any of the following: + + (a) any file in Source Code Form that results from an addition to, + deletion from, or modification of the contents of Covered + Software; or + + (b) any new file in Source Code Form that contains any Covered + Software. + +1.11. "Patent Claims" of a Contributor + means any patent claim(s), including without limitation, method, + process, and apparatus claims, in any patent Licensable by such + Contributor that would be infringed, but for the grant of the + License, by the making, using, selling, offering for sale, having + made, import, or transfer of either its Contributions or its + Contributor Version. + +1.12. "Secondary License" + means either the GNU General Public License, Version 2.0, the GNU + Lesser General Public License, Version 2.1, the GNU Affero General + Public License, Version 3.0, or any later versions of those + licenses. + +1.13. "Source Code Form" + means the form of the work preferred for making modifications. + +1.14. "You" (or "Your") + means an individual or a legal entity exercising rights under this + License. For legal entities, "You" includes any entity that + controls, is controlled by, or is under common control with You. For + purposes of this definition, "control" means (a) the power, direct + or indirect, to cause the direction or management of such entity, + whether by contract or otherwise, or (b) ownership of more than + fifty percent (50%) of the outstanding shares or beneficial + ownership of such entity. + +2. License Grants and Conditions +-------------------------------- + +2.1. Grants + +Each Contributor hereby grants You a world-wide, royalty-free, +non-exclusive license: + +(a) under intellectual property rights (other than patent or trademark) + Licensable by such Contributor to use, reproduce, make available, + modify, display, perform, distribute, and otherwise exploit its + Contributions, either on an unmodified basis, with Modifications, or + as part of a Larger Work; and + +(b) under Patent Claims of such Contributor to make, use, sell, offer + for sale, have made, import, and otherwise transfer either its + Contributions or its Contributor Version. + +2.2. Effective Date + +The licenses granted in Section 2.1 with respect to any Contribution +become effective for each Contribution on the date the Contributor first +distributes such Contribution. + +2.3. Limitations on Grant Scope + +The licenses granted in this Section 2 are the only rights granted under +this License. No additional rights or licenses will be implied from the +distribution or licensing of Covered Software under this License. +Notwithstanding Section 2.1(b) above, no patent license is granted by a +Contributor: + +(a) for any code that a Contributor has removed from Covered Software; + or + +(b) for infringements caused by: (i) Your and any other third party's + modifications of Covered Software, or (ii) the combination of its + Contributions with other software (except as part of its Contributor + Version); or + +(c) under Patent Claims infringed by Covered Software in the absence of + its Contributions. + +This License does not grant any rights in the trademarks, service marks, +or logos of any Contributor (except as may be necessary to comply with +the notice requirements in Section 3.4). + +2.4. Subsequent Licenses + +No Contributor makes additional grants as a result of Your choice to +distribute the Covered Software under a subsequent version of this +License (see Section 10.2) or under the terms of a Secondary License (if +permitted under the terms of Section 3.3). + +2.5. Representation + +Each Contributor represents that the Contributor believes its +Contributions are its original creation(s) or it has sufficient rights +to grant the rights to its Contributions conveyed by this License. + +2.6. Fair Use + +This License is not intended to limit any rights You have under +applicable copyright doctrines of fair use, fair dealing, or other +equivalents. + +2.7. Conditions + +Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted +in Section 2.1. + +3. Responsibilities +------------------- + +3.1. Distribution of Source Form + +All distribution of Covered Software in Source Code Form, including any +Modifications that You create or to which You contribute, must be under +the terms of this License. You must inform recipients that the Source +Code Form of the Covered Software is governed by the terms of this +License, and how they can obtain a copy of this License. You may not +attempt to alter or restrict the recipients' rights in the Source Code +Form. + +3.2. Distribution of Executable Form + +If You distribute Covered Software in Executable Form then: + +(a) such Covered Software must also be made available in Source Code + Form, as described in Section 3.1, and You must inform recipients of + the Executable Form how they can obtain a copy of such Source Code + Form by reasonable means in a timely manner, at a charge no more + than the cost of distribution to the recipient; and + +(b) You may distribute such Executable Form under the terms of this + License, or sublicense it under different terms, provided that the + license for the Executable Form does not attempt to limit or alter + the recipients' rights in the Source Code Form under this License. + +3.3. Distribution of a Larger Work + +You may create and distribute a Larger Work under terms of Your choice, +provided that You also comply with the requirements of this License for +the Covered Software. If the Larger Work is a combination of Covered +Software with a work governed by one or more Secondary Licenses, and the +Covered Software is not Incompatible With Secondary Licenses, this +License permits You to additionally distribute such Covered Software +under the terms of such Secondary License(s), so that the recipient of +the Larger Work may, at their option, further distribute the Covered +Software under the terms of either this License or such Secondary +License(s). + +3.4. Notices + +You may not remove or alter the substance of any license notices +(including copyright notices, patent notices, disclaimers of warranty, +or limitations of liability) contained within the Source Code Form of +the Covered Software, except that You may alter any license notices to +the extent required to remedy known factual inaccuracies. + +3.5. Application of Additional Terms + +You may choose to offer, and to charge a fee for, warranty, support, +indemnity or liability obligations to one or more recipients of Covered +Software. However, You may do so only on Your own behalf, and not on +behalf of any Contributor. You must make it absolutely clear that any +such warranty, support, indemnity, or liability obligation is offered by +You alone, and You hereby agree to indemnify every Contributor for any +liability incurred by such Contributor as a result of warranty, support, +indemnity or liability terms You offer. You may include additional +disclaimers of warranty and limitations of liability specific to any +jurisdiction. + +4. Inability to Comply Due to Statute or Regulation +--------------------------------------------------- + +If it is impossible for You to comply with any of the terms of this +License with respect to some or all of the Covered Software due to +statute, judicial order, or regulation then You must: (a) comply with +the terms of this License to the maximum extent possible; and (b) +describe the limitations and the code they affect. Such description must +be placed in a text file included with all distributions of the Covered +Software under this License. Except to the extent prohibited by statute +or regulation, such description must be sufficiently detailed for a +recipient of ordinary skill to be able to understand it. + +5. Termination +-------------- + +5.1. The rights granted under this License will terminate automatically +if You fail to comply with any of its terms. However, if You become +compliant, then the rights granted under this License from a particular +Contributor are reinstated (a) provisionally, unless and until such +Contributor explicitly and finally terminates Your grants, and (b) on an +ongoing basis, if such Contributor fails to notify You of the +non-compliance by some reasonable means prior to 60 days after You have +come back into compliance. Moreover, Your grants from a particular +Contributor are reinstated on an ongoing basis if such Contributor +notifies You of the non-compliance by some reasonable means, this is the +first time You have received notice of non-compliance with this License +from such Contributor, and You become compliant prior to 30 days after +Your receipt of the notice. + +5.2. If You initiate litigation against any entity by asserting a patent +infringement claim (excluding declaratory judgment actions, +counter-claims, and cross-claims) alleging that a Contributor Version +directly or indirectly infringes any patent, then the rights granted to +You by any and all Contributors for the Covered Software under Section +2.1 of this License shall terminate. + +5.3. In the event of termination under Sections 5.1 or 5.2 above, all +end user license agreements (excluding distributors and resellers) which +have been validly granted by You or Your distributors under this License +prior to termination shall survive termination. + +************************************************************************ +* * +* 6. Disclaimer of Warranty * +* ------------------------- * +* * +* Covered Software is provided under this License on an "as is" * +* basis, without warranty of any kind, either expressed, implied, or * +* statutory, including, without limitation, warranties that the * +* Covered Software is free of defects, merchantable, fit for a * +* particular purpose or non-infringing. The entire risk as to the * +* quality and performance of the Covered Software is with You. * +* Should any Covered Software prove defective in any respect, You * +* (not any Contributor) assume the cost of any necessary servicing, * +* repair, or correction. This disclaimer of warranty constitutes an * +* essential part of this License. No use of any Covered Software is * +* authorized under this License except under this disclaimer. * +* * +************************************************************************ + +************************************************************************ +* * +* 7. Limitation of Liability * +* -------------------------- * +* * +* Under no circumstances and under no legal theory, whether tort * +* (including negligence), contract, or otherwise, shall any * +* Contributor, or anyone who distributes Covered Software as * +* permitted above, be liable to You for any direct, indirect, * +* special, incidental, or consequential damages of any character * +* including, without limitation, damages for lost profits, loss of * +* goodwill, work stoppage, computer failure or malfunction, or any * +* and all other commercial damages or losses, even if such party * +* shall have been informed of the possibility of such damages. This * +* limitation of liability shall not apply to liability for death or * +* personal injury resulting from such party's negligence to the * +* extent applicable law prohibits such limitation. Some * +* jurisdictions do not allow the exclusion or limitation of * +* incidental or consequential damages, so this exclusion and * +* limitation may not apply to You. * +* * +************************************************************************ + +8. Litigation +------------- + +Any litigation relating to this License may be brought only in the +courts of a jurisdiction where the defendant maintains its principal +place of business and such litigation shall be governed by laws of that +jurisdiction, without reference to its conflict-of-law provisions. +Nothing in this Section shall prevent a party's ability to bring +cross-claims or counter-claims. + +9. Miscellaneous +---------------- + +This License represents the complete agreement concerning the subject +matter hereof. If any provision of this License is held to be +unenforceable, such provision shall be reformed only to the extent +necessary to make it enforceable. Any law or regulation which provides +that the language of a contract shall be construed against the drafter +shall not be used to construe this License against a Contributor. + +10. Versions of the License +--------------------------- + +10.1. New Versions + +Mozilla Foundation is the license steward. Except as provided in Section +10.3, no one other than the license steward has the right to modify or +publish new versions of this License. Each version will be given a +distinguishing version number. + +10.2. Effect of New Versions + +You may distribute the Covered Software under the terms of the version +of the License under which You originally received the Covered Software, +or under the terms of any subsequent version published by the license +steward. + +10.3. Modified Versions + +If you create software not governed by this License, and you want to +create a new license for such software, you may create and use a +modified version of this License if you rename the license and remove +any references to the name of the license steward (except to note that +such modified license differs from this License). + +10.4. Distributing Source Code Form that is Incompatible With Secondary +Licenses + +If You choose to distribute Source Code Form that is Incompatible With +Secondary Licenses under the terms of this version of the License, the +notice described in Exhibit B of this License must be attached. + +Exhibit A - Source Code Form License Notice +------------------------------------------- + + This Source Code Form is subject to the terms of the Mozilla Public + License, v. 2.0. If a copy of the MPL was not distributed with this + file, You can obtain one at http://mozilla.org/MPL/2.0/. + +If it is not possible or desirable to put the notice in a particular +file, then You may include the notice in a location (such as a LICENSE +file in a relevant directory) where a recipient would be likely to look +for such a notice. + +You may add additional accurate notices of copyright ownership. + +Exhibit B - "Incompatible With Secondary Licenses" Notice +--------------------------------------------------------- + + This Source Code Form is "Incompatible With Secondary Licenses", as + defined by the Mozilla Public License, v. 2.0. diff --git a/README.md b/README.md new file mode 100644 --- /dev/null +++ b/README.md @@ -0,0 +1,95 @@ +# webcolor-labels + +Zero-dependency, plug-and-play library that enables #hex-color syntax for your own types! + +![Demo image](https://raw.githubusercontent.com/haskell-game/webcolor-labels/refs/heads/master/images/demo.png) + +## Motivation + +[Unrestricted OverloadedLabels syntax](https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0170-unrestricted-overloadedlabels.rst) was implemented in GHC 9.6.1. It isn't hard to notice +that this syntax is a strict superset of hexadecimal CSS color syntax, a.k.a. [Web colors](https://en.wikipedia.org/wiki/Web_colors). It would be great if GUI libraries could take advantage of this +fact and allow their users to write `#f00` for the color "red," or even `#red`, right? + +That's where `webcolor-labels` comes into play. This library implements type-level string parsing and validation +and provides you an easy-to-use interface for defining an `IsLabel` instance. In fact, it's as easy as counting +one, two, three: + +```haskell +-- one +import WebColor.Labels +import GHC.OverloadedLabels + +-- two +instance IsWebColorAlpha s => IsLabel s YourColor where + fromLabel = webColorAlpha @s yourColorFromWord8 + +-- three +yourColorFromWord8 :: Word8 -> Word8 -> Word8 -> Word8 -> YourColor +yourColorFromWord8 red green blue alpha = ... +``` + +And that's all! + +## Syntax + +Allowed colors aim to follow the [Wikipedia Web Colors](https://en.wikipedia.org/wiki/Web_colors) page; here is a quick recap: + +A color is written as a hex triplet, which is a six-digit (e.g., #fa12c7) or eight-digit (e.g., #fa12c7aa) hexadecimal number. The bytes represent the red, green, blue, and optional alpha channels of the color; hence we have #rrggbbaa. + +It is possible to use the shorthand form with three and four digits: #f8c = #ff88cc and #f8c3 = #ff88cc33. + +The syntax also supports 16 basic colors for convenience: + +| Color name | Hex value | +| :--------- | :-------: | +| #white | #FFFFFF | +| #silver | #C0C0C0 | +| #gray | #808080 | +| #black | #000000 | +| #red | #FF0000 | +| #maroon | #800000 | +| #yellow | #FFFF00 | +| #olive | #808000 | +| #lime | #00FF00 | +| #green | #008000 | +| #aqua | #00FFFF | +| #teal | #008080 | +| #blue | #0000FF | +| #navy | #000080 | +| #fuchsia | #FF00FF | +| #purple | #800080 | + +Hex triplet form is case-insensitive; therefore, #fff is the same as #FFF, but basic colors are case-sensitive. +That means #red is the same as #f00, but #RED and #Red result in a compile-time error. + +## FAQ + +### I want to use this syntax with _$LIBRARYNAME_, what should I do? + +`webcolor-label`'s primary users are other library authors; therefore, you should go to the _$LIBRARYNAME_'s issue tracker and tell them that `webcolor-labels` will improve the lives of their users. + +Alternatively, you may write an orphan instance, but it's a bad idea in general and you should avoid that as much as possible. + +### `generic-lens` uses the same syntax. Does that mean it will conflict with an instance defined using `webcolor-labels`? + +No, unless you define a highly polymorphic `IsLabel` instance or your color is a type alias for a function. + +The `generic-lens` instance applies only if a function is expected in place of `#label`. Therefore, define instances with a concrete head, and everything will work smoothly. + +### But what about instances for the color types from different libraries? Might they conflict? + +No, if each instance is defined correctly. + +### I have a type class to represent colors. How can I use `#` syntax with a function that accepts my type class? + +Unfortunately, my library just doesn't fit this use case. It's the same problem as `show . read`; GHC just can't infer a type in the middle. + +### I want to use different/custom values for named colors, but `webcolor-labels` provides pre-installed values. What should I do in that case? + +You can still use type-level parsing from `webcolor-labels` and build custom routing on top of that, but you have to lower that into values yourself. + +## Contact info and acknowledgements + +If you have any questions, you can email me using `me@sandwitch.dev`. Alternatively, you can DM me on Matrix (`@root:sandwitch.dev`) or Telegram (`@sand_witch`). + +Many thanks to the Russian Haskell gamedev community, who encouraged me to convert this code into a real library and assisted with shaping the API. diff --git a/src/WebColor/Labels.hs b/src/WebColor/Labels.hs new file mode 100644 --- /dev/null +++ b/src/WebColor/Labels.hs @@ -0,0 +1,466 @@ +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE NoStarIsType #-} +{-# LANGUAGE UndecidableInstances #-} +{-# LANGUAGE TypeFamilies #-} +{-# LANGUAGE CPP #-} +{-# LANGUAGE AllowAmbiguousTypes #-} + +-- We need this to have correct links inside haddocks +{-# OPTIONS_GHC -Wno-unused-imports #-} + +-- Required to use `showType` inside haddock coments +{-# OPTIONS_GHC -Wno-unused-top-binds #-} + +{- | += Introduction and intended usage + +This library contains a small number of helpers that primarily aim +to help users construct `IsLabel` instances to use @-XOverloadedLabels@ +syntax to construct their color types using widely known web color syntax. + +There are two ways to use this API: + +1. Simple type-class-based API + +2. Advanced manual type-family-based API + +You should always prefer the simple API. + +== Simple API + +You should use the simple API to write an `IsLabel` instance for your own +type representing a color. + +Depending on whether your type supports representing the alpha channel, you should +choose between `IsWebColor` and `IsWebColorAlpha` type classes. + +Therefore, it's likely that you want to write an instance that looks like this: + +@ +data RGBA = MkRGBA { red :: `Word8`, green :: `Word8`, blue :: `Word8`, alpha :: `Word8` } + +instance `IsWebColorAlpha` s => `IsLabel` s RGBA where + `fromLabel` = `webColorAlpha` @s \r g b a -> + MkRGBA { red = r, green = g, blue = b, alpha = a } +@ + +Or this in case your type doesn't have an alpha channel: + +@ +data RGB = MkRGB { red :: `Word8`, green :: `Word8`, blue :: `Word8` } + +instance `IsWebColor` s => `IsLabel` s RGB where + `fromLabel` = `webColor` @s \r g b -> + MkRGB { red = r, green = g, blue = b } +@ + +Please do not try to use `IsWebColor` if your type can represent either +RGB or RGBA colors; use `IsWebColorAlpha` and alternate data construction +depending on the value of the alpha channel: + +@ +data Color + = MkRGB { red :: `Word8`, green :: `Word8`, blue :: `Word8` } + | MkRGBA { red :: `Word8`, green :: `Word8`, blue :: `Word8`, alpha :: `Word8` } + +instance `IsWebColorAlpha` s => `IsLabel` s RGBA where + `fromLabel` = `webColorAlpha` @s \r g b a -> + if a `==` 255 + then MkRGB { red = r, green = g, blue = b } + else MkRGBA { red = r, green = g, blue = b, alpha = a } +@ + +== Advanced API + +It's always recommended to use the simple API unless you want to drop +named colors for some reason or want to work with raw `KnownNat`s. + +There are four main type families: + +* `ParseWebColor` +* `ParseWebColorAlpha` +* `ParseWebColorMaybeAlpha` +* `ParseHexadecimalColor` + +The first two correspond to the output of `IsWebColor` and `IsWebColorAlpha` type +classes listed in the previous section. + +`ParseWebColorMaybeAlpha` allows you to alternate behavior between presence and +absence of the alpha channel in the input. Please let me know if you have a use case +for this and why you can't simply consider 255 alpha as an RGB color. + +`ParseHexadecimalColor` converts hexadecimal strings of length 3, 4, 6, and 8 into +correct color channels but doesn't accept named colors. + +In general, you give a parsing function a symbol argument and match results using the equality +operator: + +@ +f :: `ParseWebColorAlpha` s ~ '(r,g,b,a) => ... +@ + +After that, you can set various constraints on the results. For example, this is how you can +convert given values into a 32-bit number without any runtime computations: + +@ +{-# LANGUAGE DataKinds, NoStarIsType, AllowAmbiguousTypes #-} + +f :: forall s r g b a w32. + `ParseWebColorAlpha` s ~ '(r,g,b,a) => + ((r * 0x100 + g) * 0x100 + b) * 0x100 + a ~ w32 => + `KnownNat` w32 => `Word32` +f = `fromInteger` `$` `natVal` (`Proxy` @w32) +@ + +== To advanced end users + +If you're an advanced Haskell user. If you think that rules are just "recommendations." +If you're ready to face possible breakages just for slight usability improvements. +Then I present you a footgun. + +It is possible to write orphan instances for `IsWebColor` and `IsWebColorAlpha` type classes +to extend #-syntax with custom named colors, just like this: + +@ +instance `IsWebColor` "gold" where + `webColor` k = k 255 215 0 + +instance `IsWebColorAlpha` "gold" where + `webColorAlpha` k = k 255 215 0 255 +@ + +I'm not going to guarantee you anything. Enjoy! +-} + +module WebColor.Labels + ( -- * Primary API + IsWebColor(..), + IsWebColorAlpha(..), + -- * Advanced type-level API + WebColor, + WebColorAlpha, + ParseWebColor, + ParseWebColorAlpha, + WebColorParsed, + ParseWebColorMaybeAlpha, + ParseHexadecimalColor, + -- * Utility type families + -- + -- | These type families aren't required to use + -- the library, but may be useful for defining your + -- own parse routing on top of web colors + ParseHexadecimalChar, + ) where + +import Data.Proxy (Proxy (..)) +#if __GLASGOW_HASKELL__ >= 906 +import Data.Type.Equality (type (~)) +#endif +import Data.Word (Word8, Word32) +import GHC.TypeLits + (ErrorMessage (..), KnownNat, Nat, Symbol, TypeError, UnconsSymbol, natVal, type (*), type (+)) +import Prelude (Char, Maybe (..), fromInteger, ($!), ($), (==)) +import Data.Kind (Constraint) + +-- Imports for haddocks +import GHC.OverloadedLabels (IsLabel(..)) + +#if __GLASGOW_HASKELL__ >= 908 +import GHC.TypeError (Unsatisfiable) + +showType :: forall a. (Unsatisfiable (ShowType a)) => () +showType = () +#endif + +-- | Red, green, blue, and optional alpha color channels in range from 0 to 255 +type WebColorParsed = (Nat, Nat, Nat, Maybe Nat) + +-- | Parse a string containing a named color from a basic +-- palette or hexadecimal representation with an optional +-- alpha channel. +-- +-- * Named colors are always considered RGB-only: +-- +-- >>> showType @(`ParseWebColorMaybeAlpha` "red") +-- '(255, 0, 0, 'Nothing) +-- +-- >>> showType @(`ParseWebColorMaybeAlpha` "silver") +-- '(192, 192, 192, 'Nothing) +-- +-- `ParseWebColorMaybeAlpha` inherits many properties from `ParseHexadecimalColor`: +-- +-- * The difference between a `Nothing` alpha channel and @`Just` 255@ +-- is purely syntactical, and you have to tackle the difference yourself +-- * This family automatically handles shortened syntax +-- * This family throws a compile-time error when the wrong number +-- of hex characters is supplied +-- +-- Please refer to `ParseHexadecimalColor` for the examples. +type ParseWebColorMaybeAlpha :: Symbol -> WebColorParsed +type family ParseWebColorMaybeAlpha s where + ParseWebColorMaybeAlpha "white" = '(255, 255, 255, Nothing) + ParseWebColorMaybeAlpha "silver" = '(192, 192, 192, Nothing) + ParseWebColorMaybeAlpha "gray" = '(128, 128, 128, Nothing) + ParseWebColorMaybeAlpha "black" = '(0, 0, 0, Nothing) + ParseWebColorMaybeAlpha "red" = '(255, 0, 0, Nothing) + ParseWebColorMaybeAlpha "maroon" = '(128, 0, 0, Nothing) + ParseWebColorMaybeAlpha "yellow" = '(255, 255, 0, Nothing) + ParseWebColorMaybeAlpha "olive" = '(128, 128, 0, Nothing) + ParseWebColorMaybeAlpha "lime" = '(0, 255, 0, Nothing) + ParseWebColorMaybeAlpha "green" = '(0, 128, 0, Nothing) + ParseWebColorMaybeAlpha "aqua" = '(0, 255, 255, Nothing) + ParseWebColorMaybeAlpha "teal" = '(0, 128, 128, Nothing) + ParseWebColorMaybeAlpha "blue" = '(0, 0, 255, Nothing) + ParseWebColorMaybeAlpha "navy" = '(0, 0, 128, Nothing) + ParseWebColorMaybeAlpha "fuchsia" = '(255, 0, 255, Nothing) + ParseWebColorMaybeAlpha "purple" = '(128, 0, 128, Nothing) + ParseWebColorMaybeAlpha s = ParseHexadecimalColor s + +-- | Parse a string containing hexadecimal representation of a +-- color with an optional alpha channel. +-- +-- * This family doesn't handle named colors. +-- * The difference between a `Nothing` alpha channel and @`Just` 255@ +-- is purely syntactical, and you have to tackle the difference yourself: +-- +-- >>> showType @(`ParseHexadecimalColor` "fafefb") +-- '(250, 254, 251, 'Nothing) +-- +-- >>> showType @(`ParseHexadecimalColor` "fafefbff") +-- '(250, 254, 251, 'Just 255) +-- +-- * This family automatically handles shortened syntax: +-- +-- E.g. #123 is the same as #112233: +-- +-- >>> showType @(`ParseHexadecimalColor` "123") +-- '(17, 34, 51, 'Nothing) +-- +-- >>> showType @(`ParseHexadecimalColor` "112233") +-- '(17, 34, 51, 'Nothing) +-- +-- The same applies to #1234 and #11223344: +-- +-- >>> showType @(`ParseHexadecimalColor` "1234") +-- '(17, 34, 51, 'Just 68) +-- +-- >>> showType @(`ParseHexadecimalColor` "11223344") +-- '(17, 34, 51, 'Just 68) +-- +-- * This family throws a compile-time error when the wrong number +-- of hex characters is supplied: +-- +-- >>> showType @(`ParseHexadecimalColor` "1") +-- Unexpected number of hex codes +-- expected 3, 4, 6 or 8 +-- +-- >>> showType @(`ParseHexadecimalColor` "1122334455") +-- Unexpected number of hex codes +-- expected 3, 4, 6 or 8 +type ParseHexadecimalColor :: Symbol -> WebColorParsed +type family ParseHexadecimalColor s where + ParseHexadecimalColor s = ParseColorRec '[] (UnconsSymbol s) + +type ParseColorRec :: [Nat] -> Maybe (Char, Symbol) -> WebColorParsed +type family ParseColorRec color str where + ParseColorRec colors Nothing = UpgradeColor colors + ParseColorRec colors (Just '(ch, t)) = ParseColorRec (ParseHexadecimalChar ch : colors) (UnconsSymbol t) + +-- | Red, green, and blue color channels in range from 0 to 255 +type WebColor = (Nat, Nat, Nat) + +-- | Parse a string containing a named color from a basic +-- palette or hexadecimal representation without an alpha channel. +-- +-- * For convenience, a 255 alpha channel is interpreted +-- as a solid color without an alpha channel: +-- +-- >>> showType @(`ParseWebColor` "123") +-- '(17, 34, 51) +-- +-- >>> showType @(`ParseWebColor` "123f") +-- '(17, 34, 51) +-- +-- * Other alpha channel values result in a compile-time error: +-- +-- >>> showType @(`ParseWebColor` "123d") +-- Unexpected alpha channel! RGB color expected +-- +-- This family inherits many properties from `ParseWebColorMaybeAlpha`: +-- +-- * Named colors are always considered RGB-only: +-- +-- >>> showType @(`ParseWebColor` "red") +-- '(255, 0, 0) +-- +-- * This family automatically handles shortened syntax. +-- * This family throws a compile-time error when the wrong number +-- of hex characters is supplied +type ParseWebColor :: Symbol -> WebColor +type family ParseWebColor s where + ParseWebColor s = ParseRGBColorWorker (ParseWebColorMaybeAlpha s) + +type ParseRGBColorWorker :: WebColorParsed -> WebColor +type family ParseRGBColorWorker color where + ParseRGBColorWorker '(r, g, b, Nothing) = '(r, g, b) + ParseRGBColorWorker '(r, g, b, Just 255) = '(r, g, b) + ParseRGBColorWorker '(_, _, _, Just _) = TypeError (Text "Unexpected alpha channel! RGB color expected") + +-- | Red, green, blue, and alpha color channels in range from 0 to 255 +type WebColorAlpha = (Nat, Nat, Nat, Nat) + +-- | Parse a string containing a named color from a basic +-- palette or a hexadecimal representation with an optional +-- alpha channel. +-- +-- * This family converts an absence of an alpha channel into +-- the 255 value. +-- +-- >>> showType @(`ParseWebColorAlpha` "123") +-- '(17, 34, 51, 255) +-- +-- This family inherits many properties from `ParseWebColorMaybeAlpha`: +-- +-- * Named colors are always considered RGB-only and are handled the same way: +-- +-- >>> showType @(`ParseWebColorAlpha` "red") +-- '(255, 0, 0, 255) +-- +-- * This family automatically handles shortened syntax. +-- * This family throws a compile-time error when the wrong number +-- of hex characters is supplied +type ParseWebColorAlpha :: Symbol -> WebColorAlpha +type family ParseWebColorAlpha s where + ParseWebColorAlpha s = ParseRGBAColorWorker (ParseWebColorMaybeAlpha s) + +type ParseRGBAColorWorker :: WebColorParsed -> WebColorAlpha +type family ParseRGBAColorWorker color where + ParseRGBAColorWorker '(r, g, b, Nothing) = '(r, g, b, 0xFF) + ParseRGBAColorWorker '(r, g, b, Just a) = '(r, g, b, a) + +type a & b = a + +-- | Parse a type-level string containing a named color from a basic +-- palette or a hexadecimal representation and convert it into three +-- bytes representing red, green, and blue channels +-- +-- +-- * For convenience, a 255 alpha channel is interpreted +-- as a solid color without an alpha channel: +-- +-- >>> webColor @"123" (,,) +-- (17,34,51) +-- +-- >>> webColor @"123f" (,,) +-- (17,34,51) +-- +-- * Other alpha channel values result in a compile-time error: +-- +-- >>> webColor @"123d" (,,) +-- Unexpected alpha channel! RGB color expected +-- +-- * Named colors are always considered RGB-only: +-- +-- >>> webColor @"red" (,,) +-- (255,0,0) +type IsWebColor :: Symbol -> Constraint +class IsWebColor s where + -- | Parse a type-level string and give you bytes representing + -- red, green, and blue colors. + -- + -- NB: @&@ is just a type alias that should help to keep with order. + webColor :: + (Word8 & "red" -> Word8 & "green" -> Word8 & "blue" -> r) -> r + +-- | Hacky instance to avoid a warning from GHC +instance {-# OVERLAPPING #-} IsWebColor "red" where + webColor k = k 255 0 0 + +-- | Main instance where all the magic happens +instance {-# OVERLAPPABLE #-} + ( ParseWebColor s ~ '(r, g, b), + KnownNat r, KnownNat g, KnownNat b + ) => IsWebColor s where + webColor k = + k `color` Proxy @r `color` Proxy @g `color` Proxy @b + +-- | Parse a type-level string containing a named color from a basic +-- palette or a hexadecimal representation and convert it into four +-- bytes representing red, green, blue, and alpha channels +-- +-- +-- * An absent alpha channel get converted into the 255 value: +-- +-- >>> webColorAlpha @"123" (,,,) +-- (17,34,51,255) +-- +-- >>> webColorAlpha @"123f" (,,,) +-- (17,34,51,255) +-- +-- * Named colors are always considered RGB-only: +-- +-- >>> webColorAlpha @"red" (,,,) +-- (255,0,0,255) +type IsWebColorAlpha :: Symbol -> Constraint +class IsWebColorAlpha s where + -- | Parse a type-level string and give you bytes representing + -- red, green, blue, and alpha colors. + -- + -- NB: @&@ is just a type alias that should help to keep with order. + webColorAlpha :: + (Word8 & "red" -> Word8 & "green" -> Word8 & "blue" -> Word8 & "alpha" -> r) -> r + +-- | Hacky instance to avoid a warning from GHC +instance {-# OVERLAPPING #-} IsWebColorAlpha "red" where + webColorAlpha k = k 255 0 0 255 + +-- | Main instance where all the magic happens +instance {-# OVERLAPPABLE #-} + ( ParseWebColorAlpha s ~ '(r, g, b, a), + KnownNat r, KnownNat g, KnownNat b, KnownNat a + ) => IsWebColorAlpha s where + webColorAlpha k = + k `color` Proxy @r `color` Proxy @g `color` Proxy @b `color` Proxy @a + +color :: KnownNat n => (Word8 -> r) -> Proxy n -> r +color k p = k $! fromInteger (natVal p) + +type UpgradeColor :: [Nat] -> WebColorParsed +type family UpgradeColor nats where + UpgradeColor [ b, g, r ] = UpgradeColor [ b, b, g, g, r, r] + UpgradeColor [a, b, g, r ] = UpgradeColor [a, a, b, b, g, g, r, r] + UpgradeColor [ b1, b2, g1, g2, r1, r2] = '(MakeByte r2 r1, MakeByte g2 g1, MakeByte b2 b1, Nothing) + UpgradeColor [a1, a2, b1, b2, g1, g2, r1, r2] = '(MakeByte r2 r1, MakeByte g2 g1, MakeByte b2 b1, Just (MakeByte a2 a1)) + UpgradeColor _ = TypeError (Text "Unexpected number of hex codes" :$$: Text "expected 3, 4, 6 or 8") + +-- | Convert a hexadecimal character (0 .. F) into a corresponging +-- number. Case insensitive. +type ParseHexadecimalChar :: Char -> Nat +type family ParseHexadecimalChar ch where + ParseHexadecimalChar '0' = 0x0 + ParseHexadecimalChar '1' = 0x1 + ParseHexadecimalChar '2' = 0x2 + ParseHexadecimalChar '3' = 0x3 + ParseHexadecimalChar '4' = 0x4 + ParseHexadecimalChar '5' = 0x5 + ParseHexadecimalChar '6' = 0x6 + ParseHexadecimalChar '7' = 0x7 + ParseHexadecimalChar '8' = 0x8 + ParseHexadecimalChar '9' = 0x9 + ParseHexadecimalChar 'a' = 0xa + ParseHexadecimalChar 'b' = 0xb + ParseHexadecimalChar 'c' = 0xc + ParseHexadecimalChar 'd' = 0xd + ParseHexadecimalChar 'e' = 0xe + ParseHexadecimalChar 'f' = 0xf + ParseHexadecimalChar 'A' = 0xA + ParseHexadecimalChar 'B' = 0xB + ParseHexadecimalChar 'C' = 0xC + ParseHexadecimalChar 'D' = 0xD + ParseHexadecimalChar 'E' = 0xE + ParseHexadecimalChar 'F' = 0xF + ParseHexadecimalChar ch = TypeError (Text "Unable to recognize a character: " :$$: ShowType ch) + +type MakeByte :: Nat -> Nat -> Nat +type family MakeByte x y where + MakeByte x y = x * 0x10 + y diff --git a/test/Main.hs b/test/Main.hs new file mode 100644 --- /dev/null +++ b/test/Main.hs @@ -0,0 +1,92 @@ +{-# LANGUAGE OverloadedLabels #-} +{-# LANGUAGE DataKinds #-} +{-# LANGUAGE BlockArguments #-} + +{-# OPTIONS_GHC -Wno-orphans #-} + +module Main (main) where + +import WebColor.Labels +import Data.Word (Word8) +import GHC.OverloadedLabels + +import Test.Tasty +import Test.Tasty.HUnit + +instance IsWebColor "gold" where + webColor k = k 255 215 0 + +instance IsWebColorAlpha "gold" where + webColorAlpha k = k 255 215 0 255 + +data RGB = MkRGB Word8 Word8 Word8 + deriving (Show, Eq) + +instance IsWebColor s => IsLabel s RGB where + fromLabel = webColor @s MkRGB + +data RGBA = MkRGBA Word8 Word8 Word8 Word8 + deriving (Show, Eq) + +instance IsWebColorAlpha s => IsLabel s RGBA where + fromLabel = webColorAlpha @s MkRGBA + +main :: IO () +main = defaultMain $ testGroup "Tests" + [ testGroup "Named colors RGB" [ + testCase "white" do #white @?= MkRGB 255 255 255; #FFFFFF @?= MkRGB 255 255 255, + testCase "silver" do #silver @?= MkRGB 192 192 192; #C0C0C0 @?= MkRGB 192 192 192, + testCase "gray" do #gray @?= MkRGB 128 128 128; #808080 @?= MkRGB 128 128 128, + testCase "black" do #black @?= MkRGB 0 0 0; #000000 @?= MkRGB 0 0 0, + testCase "red" do #red @?= MkRGB 255 0 0; #FF0000 @?= MkRGB 255 0 0, + testCase "maroon" do #maroon @?= MkRGB 128 0 0; #800000 @?= MkRGB 128 0 0, + testCase "yellow" do #yellow @?= MkRGB 255 255 0; #FFFF00 @?= MkRGB 255 255 0, + testCase "olive" do #olive @?= MkRGB 128 128 0; #808000 @?= MkRGB 128 128 0, + testCase "lime" do #lime @?= MkRGB 0 255 0; #00FF00 @?= MkRGB 0 255 0, + testCase "green" do #green @?= MkRGB 0 128 0; #008000 @?= MkRGB 0 128 0, + testCase "aqua" do #aqua @?= MkRGB 0 255 255; #00FFFF @?= MkRGB 0 255 255, + testCase "teal" do #teal @?= MkRGB 0 128 128; #008080 @?= MkRGB 0 128 128, + testCase "blue" do #blue @?= MkRGB 0 0 255; #0000FF @?= MkRGB 0 0 255, + testCase "navy" do #navy @?= MkRGB 0 0 128; #000080 @?= MkRGB 0 0 128, + testCase "fuchsia" do #fuchsia @?= MkRGB 255 0 255; #FF00FF @?= MkRGB 255 0 255, + testCase "purple" do #purple @?= MkRGB 128 0 128; #800080 @?= MkRGB 128 0 128 + ] + , testGroup "Named colors RGBA" [ + testCase "white" do #white @?= MkRGBA 255 255 255 255; #FFFFFF @?= MkRGBA 255 255 255 255, + testCase "silver" do #silver @?= MkRGBA 192 192 192 255; #C0C0C0 @?= MkRGBA 192 192 192 255, + testCase "gray" do #gray @?= MkRGBA 128 128 128 255; #808080 @?= MkRGBA 128 128 128 255, + testCase "black" do #black @?= MkRGBA 0 0 0 255; #000000 @?= MkRGBA 0 0 0 255, + testCase "red" do #red @?= MkRGBA 255 0 0 255; #FF0000 @?= MkRGBA 255 0 0 255, + testCase "maroon" do #maroon @?= MkRGBA 128 0 0 255; #800000 @?= MkRGBA 128 0 0 255, + testCase "yellow" do #yellow @?= MkRGBA 255 255 0 255; #FFFF00 @?= MkRGBA 255 255 0 255, + testCase "olive" do #olive @?= MkRGBA 128 128 0 255; #808000 @?= MkRGBA 128 128 0 255, + testCase "lime" do #lime @?= MkRGBA 0 255 0 255; #00FF00 @?= MkRGBA 0 255 0 255, + testCase "green" do #green @?= MkRGBA 0 128 0 255; #008000 @?= MkRGBA 0 128 0 255, + testCase "aqua" do #aqua @?= MkRGBA 0 255 255 255; #00FFFF @?= MkRGBA 0 255 255 255, + testCase "teal" do #teal @?= MkRGBA 0 128 128 255; #008080 @?= MkRGBA 0 128 128 255, + testCase "blue" do #blue @?= MkRGBA 0 0 255 255; #0000FF @?= MkRGBA 0 0 255 255, + testCase "navy" do #navy @?= MkRGBA 0 0 128 255; #000080 @?= MkRGBA 0 0 128 255, + testCase "fuchsia" do #fuchsia @?= MkRGBA 255 0 255 255; #FF00FF @?= MkRGBA 255 0 255 255, + testCase "purple" do #purple @?= MkRGBA 128 0 128 255; #800080 @?= MkRGBA 128 0 128 255 + ] + , testGroup "Custom colors" [ + testCase "rgb gold" do #gold @?= MkRGB 255 215 0; #FFD700 @?= MkRGB 255 215 0, + testCase "rgba gold" do #gold @?= MkRGBA 255 215 0 255; #FFD700 @?= MkRGBA 255 215 0 255 + ] + , testGroup "hex syntax" [ + testCase "rgb 3 == 6 chars" $ #fad `rgb` #ffaadd, + testCase "rgb 3 == 8 chars" $ #fad `rgb` #ffaaddff, + testCase "rgb 4 == 8 chars" $ #eadf `rgb` #eeaaddff, + testCase "rgb 6 == 8 chars" $ #fade12 `rgb` #fade12ff, + testCase "rgba 3 == 6 chars" $ #fad `rgba` #ffaadd, + testCase "rgba 3 == 8 chars" $ #fad `rgba` #ffaaddff, + testCase "rgba 4 == 8 chars" $ #fade `rgba` #ffaaddee, + testCase "rgba 6 == 8 chars" $ #fade12 `rgba` #fade12ff + ] + ] + where + rgb :: RGB -> RGB -> Assertion + rgb = (@?=) + + rgba :: RGBA -> RGBA -> Assertion + rgba = (@?=) diff --git a/webcolor-labels.cabal b/webcolor-labels.cabal new file mode 100644 --- /dev/null +++ b/webcolor-labels.cabal @@ -0,0 +1,68 @@ +cabal-version: 3.0 + +-- Initial package description 'webcolor-labels' generated by +-- 'cabal init'. For further documentation, see: +-- http://haskell.org/cabal/users-guide/ +-- +-- The name of the package. +name: webcolor-labels + +-- PVP summary: +-+------- breaking API changes +-- | | +----- non-breaking API additions +-- | | | +--- code changes with no API change +version: 0.1.0.0 + +-- A short (one-line) description of the package. +synopsis: Plug-n-play #hex-syntax for your colors + +-- A longer description of the package. +description: + This library contains a small number of helpers that primarily aim + to help users construct `IsLabel` instances to use @-XOverloadedLabels@ + syntax to construct their color types using widely known web color syntax. + + Plug this library into your code, enable OverloadedLabels and use + #fff, #1212bc44, and even #fuchsia to create colors. + +license: MPL-2.0 +license-file: LICENSE +author: Andrei Borzenkov +maintainer: me@sandwitch.dev +homepage: https://github.com/haskell-game/webcolor-labels +bug-reports: https://github.com/haskell-game/webcolor-labels/issues + +-- A copyright notice. +-- copyright: +category: Graphics +build-type: Simple +extra-doc-files: + CHANGELOG.md + README.md + +tested-with: GHC ==9.8.4 || ==9.10.2 || ==9.12.2 + +source-repository head + type: git + location: https://github.com/haskell-game/webcolor-labels/ + +common warnings + ghc-options: -Wall + +library + import: warnings + exposed-modules: WebColor.Labels + build-depends: base >=4.16.0.0 && <5.0.0.0 + hs-source-dirs: src + default-language: GHC2021 + +test-suite webcolor-labels-test + import: warnings + default-language: GHC2021 + type: exitcode-stdio-1.0 + hs-source-dirs: test + main-is: Main.hs + build-depends: + , base >=4.18.2.1 + , tasty + , tasty-hunit + , webcolor-labels