Add setting min and max bounds limits on window

backends/opengl/window.go

@@ -79,8 +79,12 @@ type WindowConfig struct {
 	// You can make the window visible later using Window.Show().
 	Invisible bool
 
-	//SamplesMSAA specifies the level of MSAA to be used. Must be one of 0, 2, 4, 8, 16. 0 to disable.
+	// SamplesMSAA specifies the level of MSAA to be used. Must be one of 0, 2, 4, 8, 16. 0 to disable.
 	SamplesMSAA int
+
+	// BoundsLimits specifies the minimum and maximum bounds of the resizable window.
+	// If the window is full screen or not resizable, this has no effect.
+	BoundsLimits pixel.Rect
 }
 
 // Window is a window handler. Use this type to manipulate a window (input, drawing, etc.).
@@ -173,6 +177,10 @@ func NewWindow(cfg WindowConfig) (*Window, error) {
 			w.window.Show()
 		}
 
+		if !cfg.BoundsLimits.Empty() {
+			w.SetBoundsLimits(cfg.BoundsLimits)
+		}
+
 		// enter the OpenGL context
 		w.begin()
 		glhf.Init()
@@ -338,6 +346,14 @@ func (w *Window) Bounds() pixel.Rect {
 	return w.bounds
 }
 
+// SetBoundsLimits sets the minimum and maximum bounds of the window.
+// If the window is full screen or not resizable, this function does nothing.
+func (w *Window) SetBoundsLimits(limits pixel.Rect) {
+	mainthread.Call(func() {
+		w.window.SetSizeLimits(int(limits.Min.X), int(limits.Min.Y), int(limits.Max.X), int(limits.Max.Y))
+	})
+}
+
 func (w *Window) setFullscreen(monitor *Monitor) {
 	mainthread.Call(func() {
 		w.restore.xpos, w.restore.ypos = w.window.GetPos()

rectangle.go

@@ -50,6 +50,11 @@ func (r Rect) Norm() Rect {
 	}
 }
 
+// Empty returns whether the Rect's Min and Max vectors are equal to ZV.
+func (r Rect) Empty() bool {
+	return r.Min.Eq(ZV) && r.Max.Eq(ZV)
+}
+
 // W returns the width of the Rect.
 func (r Rect) W() float64 {
 	return r.Max.X - r.Min.X