add key handlers to lua

resources/slides.lua

Index: resources/slides.lua
diff --git a/resources/slides.lua b/resources/slides.lua
index 2f44e78e1bad87fb16538bf5ac8920fa23f9ab68..2f774e0de266312739b37bd971fd3b7c5e50bd77 100644
--- a/resources/slides.lua
+++ b/resources/slides.lua
@@ -2,6 +2,7 @@
 function make_paint(size, color)
     local paint = Sk.newPaint();
     paint:setAntiAlias(true)
+    paint:setSubpixelText(true)
     paint:setTextSize(size)
     paint:setColor(color)
     return paint
@@ -81,28 +82,107 @@ gSlides = {
     }
 }
 
+--------------------------------------------------------------------------------------
+
 gSlideIndex = 1
 
+function next_slide()
+    gSlideIndex = gSlideIndex + 1
+    if gSlideIndex > #gSlides then
+        gSlideIndex = 1
+    end
+end
+
+function prev_slide()
+    gSlideIndex = gSlideIndex - 1
+    if gSlideIndex < 1 then
+        gSlideIndex = #gSlides
+    end
+end
+
 --------------------------------------------------------------------------------------
 
+-- animation.proc is passed the canvas before drawing.
+-- The animation.proc returns itself or another animation (which means keep animating)
+-- or it returns nil, which stops the animation.
+--
+local gCurrAnimation
+
+function spawn_rotate_animation()
+    gCurrAnimation = {
+        angle = 0,
+        angle_delta = 5,
+        pivot_x = 320,
+        pivot_y = 240,
+        proc = function (this, canvas)
+            if this.angle >= 360 then
+                return nil
+            end
+            canvas:translate(this.pivot_x, this.pivot_y)
+            canvas:rotate(this.angle)
+            canvas:translate(-this.pivot_x, -this.pivot_y)
+
+            this.angle = this.angle + this.angle_delta
+            return this
+        end
+    }
+end
+
+function spawn_scale_animation()
+    gCurrAnimation = {
+        scale = 1,
+        scale_delta = .95,
+        scale_limit = 0.2,
+        pivot_x = 320,
+        pivot_y = 240,
+        proc = function (this, canvas)
+            if this.scale < this.scale_limit then
+                this.scale = this.scale_limit
+                this.scale_delta = 1 / this.scale_delta
+            end
+            if this.scale > 1 then
+                return nil
+            end
+            canvas:translate(this.pivot_x, this.pivot_y)
+            canvas:scale(this.scale, this.scale)
+            canvas:translate(-this.pivot_x, -this.pivot_y)
+
+            this.scale = this.scale * this.scale_delta
+            return this
+        end
+    }
+end
+
 function onDrawContent(canvas)
+    if gCurrAnimation then
+        gCurrAnimation = gCurrAnimation:proc(canvas)
+    end
+
     drawSlide(canvas, gSlides[gSlideIndex], gTemplate, gPaints)
 
-    return false -- we're not animating
+    if gCurrAnimation then
+        return true
+    else
+        return false
+    end
 end
 
 function onClickHandler(x, y)
-    if x < 100 and y < 100 then
-        onNextSlide()
-        return true
-    end
     return false
 end
 
-function onNextSlide()
-    gSlideIndex = gSlideIndex + 1
-    if gSlideIndex > #gSlides then
-        gSlideIndex = 1
+local keyProcs = {
+    n = next_slide,
+    p = prev_slide,
+    r = spawn_rotate_animation,
+    s = spawn_scale_animation,
+}
+
+function onCharHandler(uni)
+    local proc = keyProcs[uni]
+    if proc then
+        proc()
+        return true
     end
+    return false
 end
-