ui: Bug fix: Make sure current framebuffers rendered (#158)

internal/graphics/opengl/context.go

@@ -156,6 +156,10 @@ func (c *Context) TexSubImage2D(p []uint8, width, height int) {
 	gl.TexSubImage2D(mgl.TEXTURE_2D, 0, 0, 0, width, height, mgl.RGBA, mgl.UNSIGNED_BYTE, p)
 }
 
+func (c *Context) BindZeroFramebuffer() {
+	gl.BindFramebuffer(mgl.FRAMEBUFFER, mgl.Framebuffer(ZeroFramebuffer))
+}
+
 func (c *Context) NewFramebuffer(texture Texture) (Framebuffer, error) {
 	f := gl.CreateFramebuffer()
 	gl.BindFramebuffer(mgl.FRAMEBUFFER, f)

internal/ui/ui_glfw.go

@@ -157,6 +157,11 @@ func (u *userInterface) setScreenSize(width, height, scale int) bool {
 		return false
 	}
 
+	// To make sure the current existing framebuffers are rendered,
+	// swap buffers here.
+	u.context.BindZeroFramebuffer()
+	u.swapBuffers()
+
 	ch := make(chan struct{})
 	window := u.window
 	window.SetFramebufferSizeCallback(func(w *glfw.Window, width, height int) {

run.go

@@ -114,6 +114,7 @@ func Run(f func(*Image) error, width, height, scale int, title string) error {
 			return err
 		}
 
+		// Note that the current bound framebuffer must be the default one (0).
 		ui.SwapBuffers()
 
 		// Calc the current FPS.