graphics: handle default textures in high level code.

Previously each backend had to set up default textures with its own code, which needs some care for it to be robust.

src/modules/graphics/metal/Graphics.mm

@@ -281,7 +281,6 @@ Graphics::Graphics()
 	, renderBindings()
 	, uniformBufferOffset(0)
 	, defaultAttributesBuffer(nullptr)
-	, defaultTextures()
 	, families()
 { @autoreleasepool {
 	if (@available(macOS 10.15, iOS 13.0, *))
@@ -346,17 +345,6 @@ Graphics::Graphics()
 		defaultAttributesBuffer = newBuffer(attribsettings, dataformat, &defaults, sizeof(DefaultVertexAttributes), 0);
 	}
 
-	uint8 defaultpixel[] = {255, 255, 255, 255};
-	for (int i = 0; i < TEXTURE_MAX_ENUM; i++)
-	{
-		Texture::Settings settings;
-		settings.type = (TextureType) i;
-		settings.format = PIXELFORMAT_RGBA8_UNORM;
-		defaultTextures[i] = newTexture(settings);
-		Rect r = {0, 0, 1, 1};
-		defaultTextures[i]->replacePixels(defaultpixel, sizeof(defaultpixel), 0, 0, r, false);
-	}
-
 	if (batchedDrawState.vb[0] == nullptr)
 	{
 		// Initial sizes that should be good enough for most cases. It will
@@ -426,9 +414,6 @@ Graphics::~Graphics()
 	commandQueue = nil;
 	device = nil;
 
-	for (int i = 0; i < TEXTURE_MAX_ENUM; i++)
-		defaultTextures[i]->release();
-
 	for (auto &kvp : cachedSamplers)
 		CFBridgingRelease(kvp.second);
 
@@ -1144,13 +1129,6 @@ void Graphics::applyShaderUniforms(id<MTLRenderCommandEncoder> renderEncoder, lo
 
 		if (b.isMainTexture)
 		{
-			if (maintex == nullptr)
-			{
-				auto texinfo = shader->getMainTextureInfo();
-				if (texinfo != nullptr && texinfo->textureType != TEXTURE_MAX_ENUM)
-					maintex = defaultTextures[texinfo->textureType];
-			}
-
 			texture = getMTLTexture(maintex);
 			samplertex = maintex;
 		}