func (c *replacePixelsCommand) Exec(context *opengl.Context, indexOffsetInBytes int) error {
f, err := c.dst.createFramebufferIfNeeded(context)
if err != nil {
return err
}
if err := f.setAsViewport(context); err != nil {
return err
}
// Filling with non black or white color is required here for glTexSubImage2D.
// Very mysterious but this actually works (Issue #186).
// This is needed even after fixing a shader bug at f537378f2a6a8ef56e1acf1c03034967b77c7b51.
if err := context.FillFramebuffer(0, 0, 0.5, 1); err != nil {
return err
}
// This is necessary on Android. We can't call glClear just before glTexSubImage2D without
// glFlush. glTexSubImage2D didn't work without this hack at least on Nexus 5x (#211).
// This also happens when a fillCommand precedes a replacePixelsCommand.
// TODO: Can we have a better way like optimizing commands?
context.Flush()
if err := context.BindTexture(c.dst.texture.native); err != nil {
return err
}
context.TexSubImage2D(c.pixels, c.dst.width, c.dst.height)
return nil
}