From 8fa5995077d701c624e804015005c237db5aa4e1 Mon Sep 17 00:00:00 2001
From: Jannik Vogel <email@jannikvogel.de>
Date: Fri, 1 Apr 2016 01:48:36 +0200
Subject: [PATCH] OpenGL: Respect depth-read allow register

---
 .../renderer_opengl/gl_rasterizer.cpp         | 33 ++++++++++++++++---
 src/video_core/renderer_opengl/pica_to_gl.h   | 24 ++++++++++++++
 2 files changed, 53 insertions(+), 4 deletions(-)

diff --git a/src/video_core/renderer_opengl/gl_rasterizer.cpp b/src/video_core/renderer_opengl/gl_rasterizer.cpp
index 051b05cce..8348b0633 100644
--- a/src/video_core/renderer_opengl/gl_rasterizer.cpp
+++ b/src/video_core/renderer_opengl/gl_rasterizer.cpp
@@ -314,6 +314,11 @@ void RasterizerOpenGL::NotifyPicaRegisterChanged(u32 id) {
         SyncBlendFuncs();
         break;
 
+    // Stencil and depth read mask
+    case PICA_REG_INDEX(framebuffer.allow_stencil_read):
+        SyncDepthTest();
+        break;
+
     // Logic op
     case PICA_REG_INDEX(output_merger.logic_op):
         SyncLogicOp();
@@ -1032,10 +1037,30 @@ void RasterizerOpenGL::SyncStencilTest() {
 
 void RasterizerOpenGL::SyncDepthTest() {
     const auto& regs = Pica::g_state.regs;
-    state.depth.test_enabled = regs.output_merger.depth_test_enable  == 1 ||
-                               regs.output_merger.depth_write_enable == 1;
-    state.depth.test_func = regs.output_merger.depth_test_enable == 1 ?
-                            PicaToGL::CompareFunc(regs.output_merger.depth_test_func) : GL_ALWAYS;
+
+    // Enable depth test so depth writes can still occur
+    state.depth.test_enabled = GL_TRUE;
+
+    if (!regs.output_merger.depth_test_enable) {
+        state.depth.test_func = GL_ALWAYS;
+    } else {
+
+        if (!regs.framebuffer.allow_depth_read) {
+
+            // If reads are not allowed we have to patch the depth test accordingly
+            state.depth.test_func = PicaToGL::CompareXToZeroFunc(regs.output_merger.depth_test_func);
+
+            // Check if the result is known at this point, if not it depends on the framebuffer really being zero
+            if (state.depth.test_func != GL_NEVER && state.depth.test_func != GL_ALWAYS) {
+                LOG_CRITICAL(Render_OpenGL, "Can't emulate disabled read on depth yet");
+                UNIMPLEMENTED();
+            }
+
+        } else {
+            state.depth.test_func = PicaToGL::CompareFunc(regs.output_merger.depth_test_func);
+        }
+
+    }
 }
 
 void RasterizerOpenGL::SyncCombinerColor() {
diff --git a/src/video_core/renderer_opengl/pica_to_gl.h b/src/video_core/renderer_opengl/pica_to_gl.h
index fd3617d77..1cb76bd21 100644
--- a/src/video_core/renderer_opengl/pica_to_gl.h
+++ b/src/video_core/renderer_opengl/pica_to_gl.h
@@ -155,6 +155,30 @@ inline GLenum CompareFunc(Pica::Regs::CompareFunc func) {
     return compare_func_table[(unsigned)func];
 }
 
+/// Pretend we compare 'x FUNC 0' (unsigned)
+inline GLenum CompareXToZeroFunc(Pica::Regs::CompareFunc func) {
+    static const GLenum compare_func_table[] = {
+        GL_NEVER,    // CompareFunc::Never
+        GL_ALWAYS,   // CompareFunc::Always
+        GL_EQUAL,    // CompareFunc::Equal
+        GL_NOTEQUAL, // CompareFunc::NotEqual
+        GL_NEVER,    // CompareFunc::LessThan
+        GL_LEQUAL,   // CompareFunc::LessThanOrEqual
+        GL_GREATER,  // CompareFunc::GreaterThan
+        GL_ALWAYS,   // CompareFunc::GreaterThanOrEqual
+    };
+
+    // Range check table for input
+    if (static_cast<size_t>(func) >= ARRAY_SIZE(compare_func_table)) {
+        LOG_CRITICAL(Render_OpenGL, "Unknown compare function %d", func);
+        UNREACHABLE();
+
+        return GL_ALWAYS;
+    }
+
+    return compare_func_table[(unsigned)func];
+}
+
 inline GLenum StencilOp(Pica::Regs::StencilAction action) {
     static const GLenum stencil_op_table[] = {
         GL_KEEP,        // StencilAction::Keep