Break raygui.go into separate files

- per-control .go file,
- separate file for style/property stuff,
- added NumProperties enum to the list of properties for constraint checking,
- should be no code changes

raygui/progressbar.go

@@ -0,0 +1,21 @@
+package raygui
+
+import "github.com/gen2brain/raylib-go/raylib"
+
+// ProgressBar - Progress Bar element, shows current progress value
+func ProgressBar(bounds rl.Rectangle, value float32) {
+	b := bounds.ToInt32()
+	if value > 1.0 {
+		value = 1.0
+	} else if value < 0.0 {
+		value = 0.0
+	}
+
+	progressBar := rl.RectangleInt32{b.X + int32(style[ProgressbarBorderWidth]), b.Y + int32(style[ProgressbarBorderWidth]), b.Width - (int32(style[ProgressbarBorderWidth]) * 2), b.Height - (int32(style[ProgressbarBorderWidth]) * 2)}
+	progressValue := rl.RectangleInt32{b.X + int32(style[ProgressbarBorderWidth]), b.Y + int32(style[ProgressbarBorderWidth]), int32(value * float32(b.Width-int32(style[ProgressbarBorderWidth])*2)), b.Height - (int32(style[ProgressbarBorderWidth]) * 2)}
+
+	// Draw control
+	rl.DrawRectangle(b.X, b.Y, b.Width, b.Height, rl.GetColor(int32(style[ProgressbarBorderColor])))
+	rl.DrawRectangle(progressBar.X, progressBar.Y, progressBar.Width, progressBar.Height, rl.GetColor(int32(style[ProgressbarInsideColor])))
+	rl.DrawRectangle(progressValue.X, progressValue.Y, progressValue.Width, progressValue.Height, rl.GetColor(int32(style[ProgressbarProgressColor])))
+}