gpu: introduce driver.Device.PrepareTexture and use it in renderers

Vulkan textures (VkImage) are always in a particular layout, where each
layout is optimized for a particular use (transfer, sampling, compute
storage). Vulkan allows layout transitions everywhere except inside
render passes. This change adds driver.Device.PrepareTexture for
instructing the driver to switch a texture to a layout for sampling
in preparation for using it in a render pass.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

gpu/internal/d3d11/d3d11_windows.go

@@ -633,6 +633,8 @@ func (t *Texture) Release() {
 	*t = Texture{}
 }
 
+func (b *Backend) PrepareTexture(tex driver.Texture) {}
+
 func (b *Backend) BindTexture(unit int, tex driver.Texture) {
 	t := tex.(*Texture)
 	b.ctx.PSSetSamplers(uint32(unit), t.sampler)

gpu/internal/driver/driver.go

@@ -37,6 +37,7 @@ type Device interface {
 
 	BeginRenderPass(f Framebuffer, desc LoadDesc)
 	EndRenderPass()
+	PrepareTexture(t Texture)
 	BindProgram(p Program)
 	BindPipeline(p Pipeline)
 	BindTexture(unit int, t Texture)

gpu/internal/metal/metal_darwin.go

@@ -931,6 +931,8 @@ func (p *Pipeline) Release() {
 	*p = Pipeline{}
 }
 
+func (b *Backend) PrepareTexture(tex driver.Texture) {}
+
 func (b *Backend) BindTexture(unit int, tex driver.Texture) {
 	t := tex.(*Texture)
 	if enc := b.renderEnc; enc != 0 {

gpu/internal/opengl/opengl.go

@@ -1202,6 +1202,8 @@ func toTexFilter(f driver.TextureFilter) int {
 	}
 }
 
+func (b *Backend) PrepareTexture(tex driver.Texture) {}
+
 func (b *Backend) BindTexture(unit int, t driver.Texture) {
 	b.glstate.bindTexture(b.funcs, unit, t.(*texture).obj)
 }