add sudoku community example

This commit adds a simple sudoku community example that demonstrates the
use of text batching and imdraw drawing capabilities.

community/sudoku/LICENSE

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+MIT License
+
+Copyright (c) 2018 Jason Wangsadinata
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

community/sudoku/README.md

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+# Sudoku
+
+A game of Sudoku written in [Go][go].
+
+From [Wikipedia][sudoku-wiki]:
+> Sudoku (数独 sūdoku, digit-single) (/suːˈdoʊkuː/, /-ˈdɒk-/, /sə-/, originally
+> called Number Place) is a logic-based, combinatorial number-placement puzzle.
+> The objective is to fill a 9×9 grid with digits so that each column, each row,
+> and each of the nine 3×3 subgrids that compose the grid (also called "boxes",
+> "blocks", or "regions") contains all of the digits from 1 to 9. The puzzle
+> setter provides a partially completed grid, which for a well-posed puzzle has
+> a single solution.
+
+Created by [Jason Wangsadinata][jwangsadinata] using
+[Pixel][pixel].
+
+This example is kept to the bare minimum for demonstrating just the main
+concepts of using imdraw, and batch with texts. For a game with slightly more
+features, please check out [Go-Sudoku][go-sudoku]
+
+## Usage
+
+Run it the usual way:
+
+    go run sudoku.go
+
+## How to Play
+
+- *Left mouse* click to select a box.
+- *Number keys* to input a number.
+- *Space* or *Backspace* to delete a number.
+
+## Screenshots
+
+![Sudoku](sudoku.png)
+
+## Links
+
+- [Go-Sudoku][go-sudoku]
+
+[go]: https://golang.org
+[go-sudoku]: https://github.com/jwangsadinata/go-sudoku
+[jwangsadinata]: https://github.com/jwangsadinata
+[pixel]: https://github.com/faiface/pixel
+[sudoku-wiki]: https://en.wikipedia.org/wiki/Sudoku

community/sudoku/sudoku.go

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+package main
+
+import (
+	"image"
+	"os"
+	"strconv"
+
+	_ "image/png"
+
+	"github.com/faiface/pixel"
+	"github.com/faiface/pixel/imdraw"
+	"github.com/faiface/pixel/pixelgl"
+	"github.com/faiface/pixel/text"
+	"github.com/golang/freetype/truetype"
+	"golang.org/x/image/colornames"
+	"golang.org/x/image/font/gofont/goregular"
+)
+
+const (
+	width = 900
+)
+
+var input bool
+var x, y int
+
+var board = [9][9]int{}
+var puzzle = [9][9]int{
+	{6, 7, 2, 3, 4, 1, 5, 8, 9},
+	{5, 3, 4, 9, 6, 8, 1, 2, 7},
+	{8, 9, 1, 7, 5, 2, 6, 3, 4},
+	{3, 5, 6, 8, 2, 9, 4, 7, 1},
+	{7, 2, 8, 4, 1, 5, 3, 9, 6},
+	{4, 1, 9, 6, 7, 3, 8, 5, 2},
+	{1, 8, 3, 2, 9, 6, 7, 4, 5},
+	{9, 6, 7, 5, 3, 4, 2, 1, 8},
+	{2, 4, 5, 1, 8, 7, 9, 6, 3},
+}
+
+var mask = [9][9]bool{
+	{false, false, true, false, false, true, true, true, false},
+	{false, false, true, true, true, false, false, false, true},
+	{true, false, false, false, false, false, true, true, false},
+	{false, true, true, false, true, false, true, true, false},
+	{false, true, false, false, false, true, false, true, false},
+	{false, true, true, false, true, false, true, true, false},
+	{false, true, true, false, false, false, false, false, true},
+	{true, false, false, false, true, true, true, false, false},
+	{false, true, true, true, false, false, true, false, false},
+}
+
+func loadPicture(path string) (pixel.Picture, error) {
+	file, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+	img, _, err := image.Decode(file)
+	if err != nil {
+		return nil, err
+	}
+	return pixel.PictureDataFromImage(img), nil
+}
+
+func updateBoard(value int, imd *imdraw.IMDraw) {
+	board[x][y] = value
+	imd.Clear()
+	input = false
+}
+
+func run() {
+	// initialize window
+	cfg := pixelgl.WindowConfig{
+		Title:  "Sudoku",
+		Bounds: pixel.R(0, 0, width, width),
+		VSync:  true,
+	}
+	win, err := pixelgl.NewWindow(cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	// initialize imdraw
+	imd := imdraw.New(nil)
+
+	// initialize font
+	ttf, err := truetype.Parse(goregular.TTF)
+	if err != nil {
+		panic(err)
+	}
+	face := truetype.NewFace(ttf, &truetype.Options{
+		Size: 64 * width / 900,
+	})
+	atlas := text.NewAtlas(face, text.ASCII)
+
+	// initialize batch
+	batch := pixel.NewBatch(&pixel.TrianglesData{}, atlas.Picture())
+
+	// setup game
+	for i := 0; i < 9; i++ {
+		for j := 0; j < 9; j++ {
+			if mask[i][j] {
+				board[i][j] = puzzle[i][j]
+			}
+		}
+	}
+
+	for !win.Closed() {
+		// win condition
+		if board == puzzle {
+			win.SetClosed(true)
+		}
+
+		// select a box
+		if win.JustPressed(pixelgl.MouseButtonLeft) {
+			if input {
+				imd.Clear()
+			}
+			pos := win.MousePosition()
+			x = int(pos.X) / (width / 9)
+			y = int(pos.Y) / (width / 9)
+
+			if !mask[x][y] {
+				imd.Color = colornames.Paleturquoise
+				imd.Push(pixel.V(float64(x*width/9)+1, float64(y*width/9)+1),
+					pixel.V(float64((x+1)*width/9)-1, float64((y+1)*width/9)-1))
+				imd.Rectangle(0)
+				input = true
+			}
+		}
+		// act on user input
+		if input && !mask[x][y] {
+			if win.JustPressed(pixelgl.Key1) || win.JustPressed(pixelgl.KeyKP1) {
+				updateBoard(1, imd)
+			}
+			if win.JustPressed(pixelgl.Key2) || win.JustPressed(pixelgl.KeyKP2) {
+				updateBoard(2, imd)
+			}
+			if win.JustPressed(pixelgl.Key3) || win.JustPressed(pixelgl.KeyKP3) {
+				updateBoard(3, imd)
+			}
+			if win.JustPressed(pixelgl.Key4) || win.JustPressed(pixelgl.KeyKP4) {
+				updateBoard(4, imd)
+			}
+			if win.JustPressed(pixelgl.Key5) || win.JustPressed(pixelgl.KeyKP5) {
+				updateBoard(5, imd)
+			}
+			if win.JustPressed(pixelgl.Key6) || win.JustPressed(pixelgl.KeyKP6) {
+				updateBoard(6, imd)
+			}
+			if win.JustPressed(pixelgl.Key7) || win.JustPressed(pixelgl.KeyKP7) {
+				updateBoard(7, imd)
+			}
+			if win.JustPressed(pixelgl.Key8) || win.JustPressed(pixelgl.KeyKP8) {
+				updateBoard(8, imd)
+			}
+			if win.JustPressed(pixelgl.Key9) || win.JustPressed(pixelgl.KeyKP9) {
+				updateBoard(9, imd)
+			}
+			if win.JustPressed(pixelgl.Key0) || win.JustPressed(pixelgl.KeyKP0) ||
+				win.JustPressed(pixelgl.KeyBackspace) || win.JustPressed(pixelgl.KeySpace) {
+				updateBoard(0, imd)
+			}
+		}
+
+		// set up lines for drawing
+		for i := 1; i < 9; i++ {
+			imd.Color = colornames.Black
+			if i%3 == 0 {
+				imd.Push(pixel.V(float64(i*width/9), 0), pixel.V(float64(i*width/9), width))
+				imd.Line(6)
+
+				imd.Push(pixel.V(0, float64(i*width/9)), pixel.V(width, float64(i*width/9)))
+				imd.Line(6)
+			} else {
+				imd.Push(pixel.V(float64(i*width/9), 0), pixel.V(float64(i*width/9), width))
+				imd.Line(3)
+
+				imd.Push(pixel.V(0, float64(i*width/9)), pixel.V(width, float64(i*width/9)))
+				imd.Line(3)
+			}
+		}
+
+		// set up numbers for drawing
+		batch.Clear()
+		for a, sa := range board {
+			for b, sb := range sa {
+				if sb != 0 {
+					num := text.New(pixel.ZV, atlas)
+					num.WriteString(strconv.Itoa(sb))
+					num.DrawColorMask(batch,
+						pixel.IM.
+							Scaled(
+								pixel.ZV, float64(width)/900).
+							Moved(
+								pixel.V((float64(a)+0.3)*width/9,
+									(float64(b)+0.25)*width/9)),
+						colornames.Black)
+				}
+			}
+		}
+
+		// draw the scene to the window
+		win.Clear(colornames.Snow)
+		batch.Draw(win)
+		imd.Draw(win)
+
+		// update the window
+		win.Update()
+	}
+}
+
+func main() {
+	pixelgl.Run(run)
+}