Sprinkle various g_assert() around the code where gcc cannot figure out
on its own that a variable is not NULL and too much refactoring would be
needed to make it do that.
Also fix usage of g_assert_nonnull(x) to use g_assert(x) because the
first is not marked as G_GNUC_NORETURN because of course GTester
supports not aborting on aborts.
Apparently genTextures and friends only "reserves names", initializing
them will actually create them. Using glObjectLabel on textures before
initializing them will throw a GL_INVALID_VALUE error.
This fixes rendering to a texture on intel hardware. The glClear calls
would throw a GL_FRAMEBUFFER_INCOMPLETE error here, because the
gsk_gl_driver_begin_frame() call in do_render() reset the framebuffer
object in use.
Put GdkGLTexture into its own file and rename the API to
gdk_gl_texture_foo() instead of gdk_texture_foo_for_gl().
Apart from naming, no actual code changes.
Add a setter for per-renderer debug flags, and use
them where possible. Some places don't have easy access
to a renderer, so this is not complete.
Also, use g_message instead of g_print throughout.
We already ceil() the given float texture sizes here, so if they are
valid, the result should definitely be > 0. Textures with size 0 can't
be properly used, especially not as render targets, where they will
trigger an assertion failure later in a glCheckFramebuffer call.
