5 files changed, 105 insertions, 3 deletions

diff --git a/src/video_core/pica.h b/src/video_core/pica.h
index 09702d46a..065a3fd0c 100644
--- a/src/video_core/pica.h
+++ b/src/video_core/pica.h
@@ -115,7 +115,36 @@ struct Regs {
         BitField<24, 5, Semantic> map_w;
     } vs_output_attributes[7];
 
-    INSERT_PADDING_WORDS(0x11);
+    INSERT_PADDING_WORDS(0xe);
+
+    enum class ScissorMode : u32 {
+        Disabled = 0,
+        Exclude = 1, // Exclude pixels inside the scissor box
+
+        Include = 3 // Exclude pixels outside the scissor box
+    };
+
+    struct {
+        BitField<0, 2, ScissorMode> mode;
+
+        union {
+            BitField< 0, 16, u32> right;
+            BitField<16, 16, u32> bottom;
+        };
+
+        union {
+            BitField< 0, 16, u32> left_minus_1;
+            BitField<16, 16, u32> top_minus_1;
+        };
+
+        u32 GetTop() const {
+            return top_minus_1 + 1;
+        }
+
+        u32 GetLeft() const {
+            return left_minus_1 + 1;
+        }
+    } scissor_test;
 
     union {
         BitField< 0, 10, s32> x;
@@ -1328,6 +1357,7 @@ ASSERT_REG_POSITION(viewport_depth_range, 0x4d);
 ASSERT_REG_POSITION(viewport_depth_near_plane, 0x4e);
 ASSERT_REG_POSITION(vs_output_attributes[0], 0x50);
 ASSERT_REG_POSITION(vs_output_attributes[1], 0x51);
+ASSERT_REG_POSITION(scissor_test, 0x65);
 ASSERT_REG_POSITION(viewport_corner, 0x68);
 ASSERT_REG_POSITION(depthmap_enable, 0x6D);
 ASSERT_REG_POSITION(texture0_enable, 0x80);
diff --git a/src/video_core/rasterizer.cpp b/src/video_core/rasterizer.cpp
index a84170094..514d64208 100644
--- a/src/video_core/rasterizer.cpp
+++ b/src/video_core/rasterizer.cpp
@@ -338,12 +338,25 @@ static void ProcessTriangleInternal(const Shader::OutputVertex& v0,
             return;
     }
 
-    // TODO: Proper scissor rect test!
     u16 min_x = std::min({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x});
     u16 min_y = std::min({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y});
     u16 max_x = std::max({vtxpos[0].x, vtxpos[1].x, vtxpos[2].x});
     u16 max_y = std::max({vtxpos[0].y, vtxpos[1].y, vtxpos[2].y});
 
+    // Convert the scissor box coordinates to 12.4 fixed point
+    u16 scissor_left = (u16)(regs.scissor_test.GetLeft() << 4);
+    u16 scissor_top = (u16)(regs.scissor_test.GetTop() << 4);
+    u16 scissor_right = (u16)(regs.scissor_test.right << 4);
+    u16 scissor_bottom = (u16)(regs.scissor_test.bottom << 4);
+
+    if (regs.scissor_test.mode == Regs::ScissorMode::Include) {
+        // Calculate the new bounds
+        min_x = std::max(min_x, scissor_right);
+        min_y = std::max(min_y, scissor_bottom);
+        max_x = std::min(max_x, scissor_left);
+        max_y = std::min(max_y, scissor_top);
+    }
+
     min_x &= Fix12P4::IntMask();
     min_y &= Fix12P4::IntMask();
     max_x = ((max_x + Fix12P4::FracMask()) & Fix12P4::IntMask());
@@ -383,6 +396,13 @@ static void ProcessTriangleInternal(const Shader::OutputVertex& v0,
     for (u16 y = min_y + 8; y < max_y; y += 0x10) {
         for (u16 x = min_x + 8; x < max_x; x += 0x10) {
 
+            // Do not process the pixel if it's inside the scissor box and the scissor mode is set to Exclude
+            if (regs.scissor_test.mode == Regs::ScissorMode::Exclude &&
+                x >= scissor_right && x <= scissor_left &&
+                y >= scissor_bottom && y <= scissor_top) {
+                continue;
+            }
+
             // Calculate the barycentric coordinates w0, w1 and w2
             int w0 = bias0 + SignedArea(vtxpos[1].xy(), vtxpos[2].xy(), {x, y});
             int w1 = bias1 + SignedArea(vtxpos[2].xy(), vtxpos[0].xy(), {x, y});
diff --git a/src/video_core/renderer_opengl/gl_rasterizer.cpp b/src/video_core/renderer_opengl/gl_rasterizer.cpp
index 328a4f66b..14ee97d57 100644
--- a/src/video_core/renderer_opengl/gl_rasterizer.cpp
+++ b/src/video_core/renderer_opengl/gl_rasterizer.cpp
@@ -353,6 +353,15 @@ void RasterizerOpenGL::NotifyPicaRegisterChanged(u32 id) {
         SyncColorWriteMask();
         break;
 
+    // Scissor test
+    case PICA_REG_INDEX(scissor_test.mode):
+        shader_dirty = true;
+        break;
+    case PICA_REG_INDEX(scissor_test.right):
+    case PICA_REG_INDEX(scissor_test.left_minus_1):
+        SyncScissorTest();
+        break;
+
     // Logic op
     case PICA_REG_INDEX(output_merger.logic_op):
         SyncLogicOp();
@@ -1002,6 +1011,7 @@ void RasterizerOpenGL::SetShader() {
         SyncDepthOffset();
         SyncAlphaTest();
         SyncCombinerColor();
+        SyncScissorTest();
         auto& tev_stages = Pica::g_state.regs.GetTevStages();
         for (int index = 0; index < tev_stages.size(); ++index)
             SyncTevConstColor(index, tev_stages[index]);
@@ -1166,6 +1176,22 @@ void RasterizerOpenGL::SyncDepthTest() {
                             PicaToGL::CompareFunc(regs.output_merger.depth_test_func) : GL_ALWAYS;
 }
 
+void RasterizerOpenGL::SyncScissorTest() {
+    const auto& regs = Pica::g_state.regs;
+
+    if (uniform_block_data.data.scissor_right != regs.scissor_test.right ||
+        uniform_block_data.data.scissor_bottom != regs.scissor_test.bottom ||
+        uniform_block_data.data.scissor_left != regs.scissor_test.GetLeft() ||
+        uniform_block_data.data.scissor_top != regs.scissor_test.GetTop()) {
+
+        uniform_block_data.data.scissor_right = regs.scissor_test.right;
+        uniform_block_data.data.scissor_bottom = regs.scissor_test.bottom;
+        uniform_block_data.data.scissor_left = regs.scissor_test.GetLeft();
+        uniform_block_data.data.scissor_top = regs.scissor_test.GetTop();
+        uniform_block_data.dirty = true;
+    }
+}
+
 void RasterizerOpenGL::SyncCombinerColor() {
     auto combiner_color = PicaToGL::ColorRGBA8(Pica::g_state.regs.tev_combiner_buffer_color.raw);
     if (combiner_color != uniform_block_data.data.tev_combiner_buffer_color) {
diff --git a/src/video_core/renderer_opengl/gl_rasterizer.h b/src/video_core/renderer_opengl/gl_rasterizer.h
index 42482df4b..193c10291 100644
--- a/src/video_core/renderer_opengl/gl_rasterizer.h
+++ b/src/video_core/renderer_opengl/gl_rasterizer.h
@@ -56,6 +56,8 @@ union PicaShaderConfig {
 
         const auto& regs = Pica::g_state.regs;
 
+        state.scissor_test_mode = regs.scissor_test.mode;
+
         state.depthmap_enable = regs.depthmap_enable;
 
         state.alpha_test_func = regs.output_merger.alpha_test.enable ?
@@ -172,6 +174,7 @@ union PicaShaderConfig {
 
     struct State {
         Pica::Regs::CompareFunc alpha_test_func;
+        Pica::Regs::ScissorMode scissor_test_mode;
         Pica::Regs::TextureConfig::TextureType texture0_type;
         std::array<TevStageConfigRaw, 6> tev_stages;
         u8 combiner_buffer_input;
@@ -328,6 +331,10 @@ private:
         GLint alphatest_ref;
         GLfloat depth_scale;
         GLfloat depth_offset;
+        GLint scissor_right;
+        GLint scissor_bottom;
+        GLint scissor_left;
+        GLint scissor_top;
         alignas(16) GLvec3 fog_color;
         alignas(16) GLvec3 lighting_global_ambient;
         LightSrc light_src[8];
@@ -335,7 +342,7 @@ private:
         alignas(16) GLvec4 tev_combiner_buffer_color;
     };
 
-    static_assert(sizeof(UniformData) == 0x3A0, "The size of the UniformData structure has changed, update the structure in the shader");
+    static_assert(sizeof(UniformData) == 0x3B0, "The size of the UniformData structure has changed, update the structure in the shader");
     static_assert(sizeof(UniformData) < 16384, "UniformData structure must be less than 16kb as per the OpenGL spec");
 
     /// Sets the OpenGL shader in accordance with the current PICA register state
@@ -384,6 +391,9 @@ private:
     /// Syncs the depth test states to match the PICA register
     void SyncDepthTest();
 
+    /// Syncs the scissor test state to match the PICA register
+    void SyncScissorTest();
+
     /// Syncs the TEV combiner color buffer to match the PICA register
     void SyncCombinerColor();
 
diff --git a/src/video_core/renderer_opengl/gl_shader_gen.cpp b/src/video_core/renderer_opengl/gl_shader_gen.cpp
index 3bace7f01..10bb44210 100644
--- a/src/video_core/renderer_opengl/gl_shader_gen.cpp
+++ b/src/video_core/renderer_opengl/gl_shader_gen.cpp
@@ -539,6 +539,8 @@ in float texcoord0_w;
 in vec4 normquat;
 in vec3 view;
 
+in vec4 gl_FragCoord;
+
 out vec4 color;
 
 struct LightSrc {
@@ -555,6 +557,10 @@ layout (std140) uniform shader_data {
     int alphatest_ref;
     float depth_scale;
     float depth_offset;
+    int scissor_right;
+    int scissor_bottom;
+    int scissor_left;
+    int scissor_top;
     vec3 fog_color;
     vec3 lighting_global_ambient;
     LightSrc light_src[NUM_LIGHTS];
@@ -582,6 +588,16 @@ vec4 secondary_fragment_color = vec4(0.0);
         return out;
     }
 
+    // Append the scissor test
+    if (state.scissor_test_mode == Regs::ScissorMode::Include || state.scissor_test_mode == Regs::ScissorMode::Exclude) {
+        out += "if (scissor_left <= scissor_right || scissor_top <= scissor_bottom) discard;\n";
+        out += "if (";
+        // Negate the condition if we have to keep only the pixels outside the scissor box
+        if (state.scissor_test_mode == Regs::ScissorMode::Include)
+            out += "!";
+        out += "(gl_FragCoord.x >= scissor_right && gl_FragCoord.x <= scissor_left && gl_FragCoord.y >= scissor_bottom && gl_FragCoord.y <= scissor_top)) discard;\n";
+    }
+
     out += "float z_over_w = 1.0 - gl_FragCoord.z * 2.0;\n";
     out += "float depth = z_over_w * depth_scale + depth_offset;\n";
     if (state.depthmap_enable == Pica::Regs::DepthBuffering::WBuffering) {