spade-0.1.0.1: docs/graphics-and-animation.md

### Graphics and Animation

Use the #link: graphics# or #link: graphicswindow# functions to open a
graphics window and start drawing things on screen.

The origin is located at the top, left corner.

Objects are drawn in the currently draw color. Use #link: setcolor# function
to change the draw color.

Color is represented by its red, green and blue components. Each can range from
0 to 255.

##### Accelerated mode

If acceleration is enabled, output of the drawing commands are not rendered
until #link: drawscreen# is called.

##### Clearing screen

Use #link: clearscreen# function to fill the screen with the current draw color.

##### Working with screens of different resolutions

Since displays vary widely in their sizes and resolutions, dimensions that
look good on one display might look too small, or too large in a different
display resolution.

To fix this, use #link: setlogicalsize# function to correctly scale rendered
objects to look similar in different displays.

##### Keyboard input handling

The #link: getkeypresses# function can be used to get all the keys that have been pressed
since that last call of this function. This function returns a list that contains
the keycode of the keys. The keycodes can be compared using the values in #link: keycodes#
dictionary.

Example:

```
graphicswindow(500, 500)
wait(5)
-- Wait while user presses some keys
let keyspressed = getkeypresses()

if contains(keyspressed, keycodes.b) then
  -- If user pressed 'b' then set color to red
  setcolor(255, 0, 0)
else
 -- or else set color to green
  setcolor(0, 255, 0)
endif
circle(100, 100, 50)
drawscreen()
waitforkey()
```

This method is not very good to detect simultaneous key presses. For that, use
#link: getkeystate# function to capture keyboard state at a point. Then use
#link: inkeystate# function to check if a certain key was pressed at the point
of capture.

Example:

```
graphics()
loop
  let ks = getkeystate()
  -- Capture keyboard state at this point.
  -- Check if both up and left arrows are pressed in the captured state
  if (inkeystate(ks, scancodes.up) and inkeystate(ks, scancodes.left)) then
    break
  endif
endloop
```