GS/OGL: Avoid framebuffer swaps when depth is being alternated

pcsx2/GS/Renderers/OpenGL/GLState.cpp

@@ -42,8 +42,8 @@ namespace GLState
 
 	GLuint ps_ss;
 
-	GLuint rt;
-	GLuint ds;
+	GSTextureOGL* rt = nullptr;
+	GSTextureOGL* ds = nullptr;
 	GLuint tex_unit[8];
 	GLuint64 tex_handle[8];
 
@@ -72,8 +72,8 @@ namespace GLState
 
 		ps_ss = 0;
 
-		rt = 0;
-		ds = 0;
+		rt = nullptr;
+		ds = nullptr;
 		std::fill(std::begin(tex_unit), std::end(tex_unit), 0);
 		std::fill(std::begin(tex_handle), std::end(tex_handle), 0);
 

pcsx2/GS/Renderers/OpenGL/GLState.h

@@ -18,6 +18,8 @@
 #include "GS/Renderers/OpenGL/GLLoader.h"
 #include "GS/GSVector.h"
 
+class GSTextureOGL;
+
 namespace GLState
 {
 	extern GLuint fbo; // frame buffer object
@@ -44,8 +46,8 @@ namespace GLState
 
 	extern GLuint ps_ss; // sampler
 
-	extern GLuint rt; // render target
-	extern GLuint ds; // Depth-Stencil
+	extern GSTextureOGL* rt; // render target
+	extern GSTextureOGL* ds; // Depth-Stencil
 	extern GLuint tex_unit[8]; // shader input texture
 	extern GLuint64 tex_handle[8]; // shader input texture
 

pcsx2/GS/Renderers/OpenGL/GSDeviceOGL.cpp

@@ -1600,35 +1600,27 @@ bool GSDeviceOGL::DoCAS(GSTexture* sTex, GSTexture* dTex, bool sharpen_only, con
 
 void GSDeviceOGL::OMAttachRt(GSTextureOGL* rt)
 {
-	GLuint id = 0;
 	if (rt)
-	{
 		rt->WasAttached();
-		id = rt->GetID();
-	}
 
-	if (GLState::rt != id)
+	if (GLState::rt != rt)
 	{
-		GLState::rt = id;
-		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, id, 0);
+		GLState::rt = rt;
+		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, rt ? rt->GetID() : 0, 0);
 	}
 }
 
 void GSDeviceOGL::OMAttachDs(GSTextureOGL* ds)
 {
-	GLuint id = 0;
 	if (ds)
-	{
 		ds->WasAttached();
-		id = ds->GetID();
-	}
 
-	if (GLState::ds != id)
+	if (GLState::ds != ds)
 	{
-		GLState::ds = id;
+		GLState::ds = ds;
 
 		const GLenum target = m_features.framebuffer_fetch ? GL_DEPTH_ATTACHMENT : GL_DEPTH_STENCIL_ATTACHMENT;
-		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, target, GL_TEXTURE_2D, id, 0);
+		glFramebufferTexture2D(GL_DRAW_FRAMEBUFFER, target, GL_TEXTURE_2D, ds ? ds->GetID() : 0, 0);
 	}
 }
 
@@ -1657,6 +1649,14 @@ void GSDeviceOGL::OMSetColorMaskState(OMColorMaskSelector sel)
 	}
 }
 
+void GSDeviceOGL::OMUnbindTexture(GSTextureOGL* tex)
+{
+	if (GLState::rt == tex)
+		OMAttachRt();
+	if (GLState::ds == tex)
+		OMAttachDs();
+}
+
 void GSDeviceOGL::OMSetBlendState(bool enable, GLenum src_factor, GLenum dst_factor, GLenum op, bool is_constant, u8 constant)
 {
 	if (enable)
@@ -1968,8 +1968,21 @@ void GSDeviceOGL::RenderHW(GSHWDrawConfig& config)
 		s_gl_blend_factors[config.blend.dst_factor], s_gl_blend_ops[config.blend.op],
 		config.blend.constant_enable, config.blend.constant);
 	OMSetColorMaskState(config.colormask);
+
+	// avoid changing framebuffer just to switch from rt+depth to rt and vice versa
+	GSTexture* draw_rt = hdr_rt ? hdr_rt : config.rt;
+	GSTexture* draw_ds = config.ds;
+	if (!draw_ds && GLState::ds && GLState::rt == draw_rt && config.tex != GLState::ds &&
+		GLState::ds->GetSize() == draw_rt->GetSize())
+	{
+		// should already be always-pass.
+		draw_ds = GLState::ds;
+		config.depth.ztst = ZTST_ALWAYS;
+		config.depth.zwe = false;
+	}
+
+	OMSetRenderTargets(draw_rt, draw_ds, &config.scissor);
 	SetupOM(config.depth);
-	OMSetRenderTargets(hdr_rt ? hdr_rt : config.rt, config.ds, &config.scissor);
 
 	SendHWDraw(config, psel.ps.IsFeedbackLoop());
 

pcsx2/GS/Renderers/OpenGL/GSDeviceOGL.h

@@ -357,6 +357,7 @@ public:
 	void OMSetBlendState(bool enable = false, GLenum src_factor = GL_ONE, GLenum dst_factor = GL_ZERO, GLenum op = GL_FUNC_ADD, bool is_constant = false, u8 constant = 0);
 	void OMSetRenderTargets(GSTexture* rt, GSTexture* ds, const GSVector4i* scissor = NULL);
 	void OMSetColorMaskState(OMColorMaskSelector sel = OMColorMaskSelector());
+	void OMUnbindTexture(GSTextureOGL* tex);
 
 	bool CreateTextureFX();
 	std::string GetShaderSource(const std::string_view& entry, GLenum type, const std::string_view& common_header, const std::string_view& glsl_h_code, const std::string_view& macro_sel);

pcsx2/GS/Renderers/OpenGL/GSTextureOGL.cpp

@@ -174,12 +174,10 @@ GSTextureOGL::GSTextureOGL(Type type, int width, int height, int levels, Format
 
 GSTextureOGL::~GSTextureOGL()
 {
-	/* Unbind the texture from our local state */
+	// Textures aren't cleared from attachments on deletion.
+	GSDeviceOGL::GetInstance()->OMUnbindTexture(this);
 
-	if (m_texture_id == GLState::rt)
-		GLState::rt = 0;
-	if (m_texture_id == GLState::ds)
-		GLState::ds = 0;
+	// But they are unbound.
 	for (GLuint& tex : GLState::tex_unit)
 	{
 		if (m_texture_id == tex)