Milestone: Screenshot to PNG Test Feature

.gitignore

@@ -1 +1,2 @@
 fonts/
+screenshot-*.png

Changes.md

@@ -0,0 +1,24 @@
+# Changes
+
+## v0.0.1-alpha - June 17 2018
+
+* Add a debug overlay that shows FPS, coordinates, and useful info.
+* Add FPS throttling to target 60 frames per second.
+* Add `F12` for Screenshot key which saves the in-memory representation of
+  the pixels you've drawn to disk as a PNG image.
+* Smoothly connect dots between periods where the mouse button was held down
+  but was moving too fast.
+
+## v0.0.0-alpha
+
+* Basic SDL canvas that draws pixels when you click and/or drag.
+* The lines drawn aren't smooth, because the mouse cursor moves too fast.
+
+### Screenshot Feature
+
+Pressing `F12` takes a screenshot and saves it on disk as a PNG.
+
+It does **NOT** read the SDL canvas data for this, though. It uses an
+internal representation of the pixels you've been drawing, and writes that
+to the PNG. This is important because that same pixel data will be used for
+the custom level format.

README.md

@@ -7,9 +7,16 @@ As a rough idea of the milestones needed for this game to work:
 ## SDL Paint Program
 
 * [x] Create a basic SDL window that you can click on to color pixels.
-  * [ ] Connect the pixels while the mouse is down to cover gaps.
-* [ ] Implement a "screenshot" button that translates the canvas to a PNG
+  * [x] Connect the pixels while the mouse is down to cover gaps.
+* [x] Implement a "screenshot" button that translates the canvas to a PNG
   image on disk.
+  * `F12` key to take a screenshot of your drawing.
+  * It reproduces a PNG image using its in-memory knowledge of the pixels you
+    have drawn, *not* by reading the SDL canvas. This will be important for
+    making the custom level format later.
+  * The PNG I draw looks slightly different to what you see on the SDL canvas;
+    maybe difference between `Renderer.DrawLine()` and my own algorithm or
+    the anti-aliasing.
 * [ ] Create a custom map file format (protobufs maybe) and "screenshot" the
   canvas into this custom file format.
 * [ ] Make the program able to read this file format and reproduce the same

doodle.go

@@ -13,10 +13,10 @@ import (
 
 const (
 	// Version number.
-	Version = "0.0.0-alpha"
+	Version = "0.0.1-alpha"
 
 	// TargetFPS is the frame rate to cap the game to.
-	TargetFPS = uint32(1000 / 60) // 60 FPS
+	TargetFPS = 1000 / 60 // 60 FPS
 
 	// Millisecond64 is a time.Millisecond casted to float64.
 	Millisecond64 = float64(time.Millisecond)
@@ -104,20 +104,27 @@ func (d *Doodle) Run() error {
 
 	log.Info("Enter Main Loop")
 	for d.running {
+		d.ticks++
+
 		// Draw a frame and log how long it took.
 		start := time.Now()
 		err = d.Loop()
-		d.ticks++
-		elapsed := time.Now().Sub(start)
-
-		tmp := elapsed / time.Millisecond
-		delay := TargetFPS - uint32(tmp)
-		sdl.Delay(delay)
-
-		d.TrackFPS(delay)
 		if err != nil {
 			return err
 		}
+
+		elapsed := time.Now().Sub(start)
+
+		// Delay to maintain the target frames per second.
+		tmp := elapsed / time.Millisecond
+		var delay uint32
+		if TargetFPS-int(tmp) > 0 { // make sure it won't roll under
+			delay = uint32(TargetFPS - int(tmp))
+		}
+		sdl.Delay(delay)
+
+		// Track how long this frame took to measure FPS over time.
+		d.TrackFPS(delay)
 	}
 
 	log.Warn("Main Loop Exited! Shutting down...")
@@ -143,6 +150,7 @@ func (p Pixel) String() string {
 // Grid is a 2D grid of pixels in X,Y notation.
 type Grid map[Pixel]interface{}
 
+// TODO: a linked list instead of a slice
 var pixelHistory []Pixel
 
 // Loop runs one loop of the game engine.
@@ -154,6 +162,12 @@ func (d *Doodle) Loop() error {
 		return err
 	}
 
+	// Taking a screenshot?
+	if ev.ScreenshotKey.Pressed() {
+		log.Info("Taking a screenshot")
+		d.Screenshot()
+	}
+
 	// Clear the canvas and fill it with white.
 	d.renderer.SetDrawColor(255, 255, 255, 255)
 	d.renderer.Clear()
@@ -161,16 +175,26 @@ func (d *Doodle) Loop() error {
 	// Clicking? Log all the pixels while doing so.
 	if ev.Button1.Now {
 		pixel := Pixel{
-			start: ev.Button1.Now && !ev.Button1.Last,
+			start: ev.Button1.Pressed(),
 			x:     ev.CursorX.Now,
 			y:     ev.CursorY.Now,
-			dx:    ev.CursorX.Last,
-			dy:    ev.CursorY.Last,
+			dx:    ev.CursorX.Now,
+			dy:    ev.CursorY.Now,
 		}
 
 		// Append unique new pixels.
 		if len(pixelHistory) == 0 || pixelHistory[len(pixelHistory)-1] != pixel {
+			// If not a start pixel, make the delta coord the previous one.
+			if !pixel.start && len(pixelHistory) > 0 {
+				prev := pixelHistory[len(pixelHistory)-1]
+				pixel.dx = prev.x
+				pixel.dy = prev.y
+			}
+
 			pixelHistory = append(pixelHistory, pixel)
+
+			// Save in the pixel canvas map.
+			d.canvas[pixel] = nil
 		}
 	}
 

events/events.go

@@ -10,21 +10,25 @@ import (
 // State keeps track of event states.
 type State struct {
 	// Mouse buttons.
-	Button1 *BoolFrameState
-	Button2 *BoolFrameState
+	Button1 *BoolTick
+	Button2 *BoolTick
+
+	// Screenshot key.
+	ScreenshotKey *BoolTick
 
 	// Cursor positions.
-	CursorX *Int32FrameState
-	CursorY *Int32FrameState
+	CursorX *Int32Tick
+	CursorY *Int32Tick
 }
 
 // New creates a new event state manager.
 func New() *State {
 	return &State{
-		Button1: &BoolFrameState{},
-		Button2: &BoolFrameState{},
-		CursorX: &Int32FrameState{},
-		CursorY: &Int32FrameState{},
+		Button1:       &BoolTick{},
+		Button2:       &BoolTick{},
+		ScreenshotKey: &BoolTick{},
+		CursorX:       &Int32Tick{},
+		CursorY:       &Int32Tick{},
 	}
 }
 
@@ -96,6 +100,14 @@ func (s *State) Poll(ticks uint64) (*State, error) {
 			log.Debug("[%d ms] tick:%d Keyboard  type:%d  sym:%c  modifiers:%d  state:%d  repeat:%d\n",
 				t.Timestamp, ticks, t.Type, t.Keysym.Sym, t.Keysym.Mod, t.State, t.Repeat,
 			)
+			if t.Repeat == 1 {
+				continue
+			}
+
+			switch t.Keysym.Scancode {
+			case sdl.SCANCODE_F12:
+				s.ScreenshotKey.Push(t.State == 1)
+			}
 		}
 	}
 

events/types.go

@@ -1,25 +1,30 @@
 package events
 
-// BoolFrameState holds boolean state between this frame and the previous.
-type BoolFrameState struct {
+// BoolTick holds boolean state between this frame and the previous.
+type BoolTick struct {
 	Now  bool
 	Last bool
 }
 
-// Int32FrameState manages int32 state between this frame and the previous.
-type Int32FrameState struct {
+// Int32Tick manages int32 state between this frame and the previous.
+type Int32Tick struct {
 	Now  int32
 	Last int32
 }
 
 // Push a bool state, copying the current Now value to Last.
-func (bs *BoolFrameState) Push(v bool) {
+func (bs *BoolTick) Push(v bool) {
 	bs.Last = bs.Now
 	bs.Now = v
 }
 
+// Pressed returns true if the button was pressed THIS tick.
+func (bs *BoolTick) Pressed() bool {
+	return bs.Now && !bs.Last
+}
+
 // Push an int32 state, copying the current Now value to Last.
-func (is *Int32FrameState) Push(v int32) {
+func (is *Int32Tick) Push(v int32) {
 	is.Last = is.Now
 	is.Now = v
 }

fps.go

@@ -27,7 +27,7 @@ func (d *Doodle) DrawDebugOverlay() {
 	}
 
 	text := fmt.Sprintf(
-		"FPS: %d (%dms)    (X,Y)=(%d,%d)  canvas=%d",
+		"FPS: %d (%dms)  (%d,%d)  size=%d  F12=screenshot",
 		fpsCurrent,
 		fpsSkipped,
 		d.events.CursorX.Now,

screenshot.go

@@ -0,0 +1,75 @@
+package doodle
+
+import (
+	"fmt"
+	"image"
+	"image/png"
+	"math"
+	"os"
+	"time"
+)
+
+// Screenshot saves the level canvas to disk as a PNG image.
+func (d *Doodle) Screenshot() {
+	screenshot := image.NewRGBA(image.Rect(0, 0, int(d.width), int(d.height)))
+
+	// White-out the image.
+	for x := 0; x < int(d.width); x++ {
+		for y := 0; y < int(d.height); y++ {
+			screenshot.Set(x, y, image.White)
+		}
+	}
+
+	// Fill in the dots we drew.
+	for pixel := range d.canvas {
+		// A line or a dot?
+		if pixel.x == pixel.dx && pixel.y == pixel.dy {
+			screenshot.Set(int(pixel.x), int(pixel.y), image.Black)
+		} else {
+			// Draw a line. TODO: get this into its own function!
+			// https://en.wikipedia.org/wiki/Digital_differential_analyzer_(graphics_algorithm)
+			var (
+				x1 = pixel.x
+				x2 = pixel.dx
+				y1 = pixel.y
+				y2 = pixel.dy
+			)
+			var (
+				dx = float64(x2 - x1)
+				dy = float64(y2 - y1)
+			)
+			var step float64
+			if math.Abs(dx) >= math.Abs(dy) {
+				step = math.Abs(dx)
+			} else {
+				step = math.Abs(dy)
+			}
+
+			dx = dx / step
+			dy = dy / step
+			x := float64(x1)
+			y := float64(y1)
+			for i := 0; i <= int(step); i++ {
+				screenshot.Set(int(x), int(y), image.Black)
+				x += dx
+				y += dy
+			}
+		}
+
+	}
+
+	filename := fmt.Sprintf("screenshot-%s.png",
+		time.Now().Format("2006-01-02T15-04-05"),
+	)
+	fh, err := os.Create(filename)
+	if err != nil {
+		log.Error(err.Error())
+		return
+	}
+	defer fh.Close()
+
+	if err := png.Encode(fh, screenshot); err != nil {
+		log.Error(err.Error())
+		return
+	}
+}