Add color blind accessibility filter

main.lua

@@ -31,6 +31,7 @@ function love.load()
 	_initGridVars()
 	_initSounds()
 	_initGlobalColors()
+	_initAccessibility()
 	gameWorld = World:new()
 	_initLevelEditor()
 
@@ -116,16 +117,42 @@ function love.draw()
 	love.graphics.pop()
 	love.graphics.setCanvas()
 
+	-- Collect every visible layer before the accessibility pass.  Applying the
+	-- shader here also covers the editor sidebar, FPS display, and dialogue,
+	-- rather than only recolouring the room sprites.
+	love.graphics.setCanvas(presentationCanvas)
+	love.graphics.clear()
 	love.graphics.setBlendMode("alpha")
 	love.graphics.setColor(1, 1, 1, 1)
 	love.graphics.draw(finalCanvas, 0, 0)
 	love.graphics.draw(sideBarCanvas, sideBarBox.x, sideBarBox.y)
 	love.graphics.print("Current FPS: "..tostring(love.timer.getFPS( )), 10, 10)
-
 	Dialogue.draw()
+	love.graphics.setCanvas()
+
+	love.graphics.setColor(1, 1, 1, 1)
+	local filter = accessibilityModes[accessibilityModeIndex]
+	if filter.shader then
+		filter.shader:send("accessibilityTime", love.timer.getTime())
+		love.graphics.setShader(filter.shader)
+	end
+	love.graphics.draw(presentationCanvas, 0, 0)
+	love.graphics.setShader()
+
+	if accessibilityMessage and love.timer.getTime() < accessibilityMessageExpires then
+		love.graphics.setColor(1, 1, 1, 1)
+		love.graphics.printf(accessibilityMessage, 0, 30, love.graphics.getWidth(), "center")
+	end
 end
 
 function love.keypressed(key)
+	-- Available even while a dialogue is open, so the player never has to
+	-- dismiss something important just to change the colour treatment.
+	if key == "f4" then
+		cycleAccessibilityMode()
+		return
+	end
+
 	-- Talking to a sign captures input: navigate/choose, don't move the player.
 	if Dialogue.isOpen() then
 		Dialogue.keypressed(key)
@@ -237,6 +264,7 @@ end
 function _initCanvases()
 	gameCanvas = love.graphics.newCanvas()
 	finalCanvas = love.graphics.newCanvas()
+	presentationCanvas = love.graphics.newCanvas()
 	sideBarCanvas = love.graphics.newCanvas(math.max(1, sideBarBox.w), math.max(1, sideBarBox.h))
 	sideBarCanvas:setFilter("nearest", "nearest") -- never average when sampled
 end
@@ -253,6 +281,37 @@ function _initGlobalColors()
 	gColor.red, gColor.green, gColor.blue, gColor.white = Color:new("red"), Color:new("green"), Color:new("blue"), Color:new("white")
 end
 
+function _initAccessibility()
+	accessibilityModes = {
+		{ id = "normal", label = "Normal", shader = nil },
+		{ id = "deuteranopia", label = "Deuteranopia", shader = accessibilityColorShader },
+	}
+	accessibilityModeIndex = 1
+
+	local savedMode = love.filesystem.read("accessibility_mode.txt")
+	if savedMode then
+		savedMode = savedMode:match("[%w_]+")
+		if savedMode == "deuteranopia_high_contrast" then savedMode = "deuteranopia" end
+		for index, mode in ipairs(accessibilityModes) do
+			if mode.id == savedMode then
+				accessibilityModeIndex = index
+				break
+			end
+		end
+	end
+	local mode = accessibilityModes[accessibilityModeIndex]
+	accessibilityMessage = "Color filter: " .. mode.label .. "  (F4 to change)"
+	accessibilityMessageExpires = love.timer.getTime() + 4
+end
+
+function cycleAccessibilityMode()
+	accessibilityModeIndex = accessibilityModeIndex % #accessibilityModes + 1
+	local mode = accessibilityModes[accessibilityModeIndex]
+	love.filesystem.write("accessibility_mode.txt", mode.id)
+	accessibilityMessage = "Color filter: " .. mode.label .. "  (F4 to change)"
+	accessibilityMessageExpires = love.timer.getTime() + 2.5
+end
+
 function _initSounds()
 	staticWave = sfxr.newSound()
 	staticWave.waveform = sfxr.WAVEFORM.NOISE -- was `wavetype = 3`; field renamed in this sfxr