drawing basic shapes

1 files changed, 109 insertions, 0 deletions

diff --git a/examples/shapes/main.go b/examples/shapes/main.go
new file mode 100644
index 0000000..c03071f
--- /dev/null
+++ b/examples/shapes/main.go
@@ -0,0 +1,109 @@
+// Example shapes shows how to draw basic shapes into a window.
+// It can be considered the Go aequivalent of
+// https://x.org/releases/X11R7.5/doc/libxcb/tutorial/#drawingprim
+// Four points, a single polyline, two line segments,
+// two rectangle and two arcs are drawn.
+package main
+
+import (
+	"fmt"
+
+	"github.com/jezek/xgb"
+	"github.com/jezek/xgb/xproto"
+)
+
+func main() {
+	X, err := xgb.NewConn()
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	defer X.Close()
+
+	setup := xproto.Setup(X)
+	screen := setup.DefaultScreen(X)
+	wid, _ := xproto.NewWindowId(X)
+	draw := xproto.Drawable(wid)
+
+	// Create the window
+	xproto.CreateWindow(X, screen.RootDepth, wid, screen.Root,
+		0, 0, 500, 500, 8, // X, Y, width, height, *border width*
+		xproto.WindowClassInputOutput, screen.RootVisual,
+		xproto.CwBackPixel | xproto.CwEventMask,
+		[]uint32{ screen.WhitePixel, xproto.EventMaskStructureNotify | xproto.EventMaskExposure })
+
+	// Map the window on the screen
+	xproto.MapWindow(X, wid)
+
+	// Up to here everything is the same as in the `create-window` example.
+	// We opened a connection, created and mapped the window.
+	// Note how this time the border width is set to 8 instead of 0.
+	//
+	// But this time we'll be drawing some basic shapes:
+
+	// Create black (foreground) graphic context
+	foreground, _ := xproto.NewGcontextId(X)
+	mask := uint32(xproto.GcForeground | xproto.GcGraphicsExposures)
+	values := []uint32{screen.BlackPixel, 0}
+	xproto.CreateGC(X, foreground, draw, mask, values)
+
+	points := []xproto.Point{
+		{X: 10, Y: 10},
+		{X: 20, Y: 10},
+		{X: 30, Y: 10},
+		{X: 40, Y: 10},
+	}
+
+	// A polyline is essientially a line with multiple points:
+	polyline := []xproto.Point{
+		{X: 50, Y: 10},
+		{X: 5, Y: 20}, // rest of points are relative
+		{X: 25, Y: -20},
+		{X: 10, Y: 10},
+	}
+
+	segments := []xproto.Segment{
+		{X1: 100, Y1: 10, X2: 140, Y2: 30},
+		{X1: 110, Y1: 25, X2: 130, Y2: 60},
+	}
+
+	// Rectangles have a start coordinate (upper left) and width and height.
+	rectangles := []xproto.Rectangle{
+		{X: 10, Y: 50, Width: 40, Height: 20},
+		{X: 80, Y: 50, Width: 10, Height: 40},
+	}
+
+	arcs := []xproto.Arc{
+		{X: 10, Y: 100, Width: 60, Height: 40, Angle1: 0, Angle2: 90 << 6},
+		{X: 90, Y: 100, Width: 55, Height: 40, Angle1: 0, Angle2: 270 << 6},
+	}
+
+	for {
+		evt, err := X.WaitForEvent()
+		switch evt.(type) {
+		case xproto.ExposeEvent:
+			/* We draw the points */
+			xproto.PolyPoint(X, xproto.CoordModeOrigin, draw, foreground, points)
+
+			/* We draw the polygonal line */
+			xproto.PolyLine(X, xproto.CoordModePrevious, draw, foreground, polyline)
+
+			/* We draw the segments */
+			xproto.PolySegment(X, draw, foreground, segments)
+
+			/* We draw the rectangles */
+			xproto.PolyRectangle(X, draw, foreground, rectangles)
+
+			/* We draw the arcs */
+			xproto.PolyArc(X, draw, foreground, arcs)
+
+		case xproto.DestroyNotifyEvent:
+			return
+		}
+
+		if err != nil {
+			fmt.Println(err)
+			return
+		}
+	}
+}