opengl: Bug fix: Reset the bound framebuffer after deletion (#227)

internal/graphics/opengl/context.go

@@ -38,8 +38,8 @@ type Context struct {
 }
 
 func (c *Context) bindFramebuffer(f Framebuffer) {
-	// TODO: This is a temporal hack to pass the tests.
-	// Fix the bug (#227).
+	if c.lastFramebuffer != f {
 		c.bindFramebufferImpl(f)
 		c.lastFramebuffer = f
 	}
+}

internal/graphics/opengl/context_desktop.go

@@ -247,6 +247,12 @@ func (c *Context) FillFramebuffer(r, g, b, a float64) error {
 func (c *Context) DeleteFramebuffer(f Framebuffer) {
 	c.RunOnContextThread(func() error {
 		ff := uint32(f)
+		// If a framebuffer to be delted is bound, a newly bound framebuffer
+		// will be a default framebuffer.
+		// https://www.khronos.org/opengles/sdk/docs/man/xhtml/glDeleteFramebuffers.xml
+		if c.lastFramebuffer == f {
+			c.lastFramebuffer = ZeroFramebuffer
+		}
 		gl.DeleteFramebuffers(1, &ff)
 		return nil
 	})

internal/graphics/opengl/context_js.go

@@ -223,6 +223,12 @@ func (c *Context) FillFramebuffer(r, g, b, a float64) error {
 
 func (c *Context) DeleteFramebuffer(f Framebuffer) {
 	gl := c.gl
+	// If a framebuffer to be delted is bound, a newly bound framebuffer
+	// will be a default framebuffer.
+	// https://www.khronos.org/opengles/sdk/docs/man/xhtml/glDeleteFramebuffers.xml
+	if c.lastFramebuffer == f {
+		c.lastFramebuffer = ZeroFramebuffer
+	}
 	gl.DeleteFramebuffer(f.Object)
 }
 

internal/graphics/opengl/context_mobile.go

@@ -199,6 +199,12 @@ func (c *Context) FillFramebuffer(r, g, b, a float64) error {
 
 func (c *Context) DeleteFramebuffer(f Framebuffer) {
 	gl := c.gl
+	// If a framebuffer to be delted is bound, a newly bound framebuffer
+	// will be a default framebuffer.
+	// https://www.khronos.org/opengles/sdk/docs/man/xhtml/glDeleteFramebuffers.xml
+	if c.lastFramebuffer == f {
+		c.lastFramebuffer = ZeroFramebuffer
+	}
 	gl.DeleteFramebuffer(mgl.Framebuffer(f))
 }