prevent bleeding in screen texture

fixes #920

3 files changed, 52 insertions, 28 deletions

diff --git a/src/GPU_OpenGL.cpp b/src/GPU_OpenGL.cpp
index 0c6cf00..f60ca97 100644
--- a/src/GPU_OpenGL.cpp
+++ b/src/GPU_OpenGL.cpp
@@ -40,7 +40,13 @@ GLuint Comp3DXPosLoc[1];
 
 GLuint CompVertexBufferID;
 GLuint CompVertexArrayID;
-float CompVertices[2 * 3*2 * 2]; // position
+
+struct CompVertex
+{
+    float Position[2];
+    float Texcoord[2];
+};
+CompVertex CompVertices[2 * 3*2];
 
 GLuint CompScreenInputTex;
 GLuint CompScreenOutputTex;
@@ -59,6 +65,7 @@ bool Init()
         GLint uni_id;
 
         glBindAttribLocation(CompShader[i][2], 0, "vPosition");
+        glBindAttribLocation(CompShader[i][2], 1, "vTexcoord");
         glBindFragDataLocation(CompShader[i][2], 0, "oColor");
 
         if (!OpenGL::LinkShaderProgram(CompShader[i]))
@@ -74,25 +81,29 @@ bool Init()
         glUniform1i(uni_id, 1);
     }
 
-#define SETVERTEX(i, x, y) \
-    CompVertices[2*(i) + 0] = x; \
-    CompVertices[2*(i) + 1] = y;
+    // all this mess is to prevent bleeding
+#define SETVERTEX(i, x, y, offset) \
+    CompVertices[i].Position[0] = x; \
+    CompVertices[i].Position[1] = y + offset; \
+    CompVertices[i].Texcoord[0] = (x + 1.f) * (256.f / 2.f); \
+    CompVertices[i].Texcoord[1] = (y + 1.f) * (384.f / 2.f)
 
+    const float padOffset = 1.f/(192*2.f+2.f)*2.f;
     // top screen
-    SETVERTEX(0, -1, 1);
-    SETVERTEX(1, 1, 0);
-    SETVERTEX(2, 1, 1);
-    SETVERTEX(3, -1, 1);
-    SETVERTEX(4, -1, 0);
-    SETVERTEX(5, 1, 0);
+    SETVERTEX(0, -1, 1, 0);
+    SETVERTEX(1, 1, 0, padOffset);
+    SETVERTEX(2, 1, 1, 0);
+    SETVERTEX(3, -1, 1, 0);
+    SETVERTEX(4, -1, 0, padOffset);
+    SETVERTEX(5, 1, 0, padOffset);
 
     // bottom screen
-    SETVERTEX(6, -1, 0);
-    SETVERTEX(7, 1, -1);
-    SETVERTEX(8, 1, 0);
-    SETVERTEX(9, -1, 0);
-    SETVERTEX(10, -1, -1);
-    SETVERTEX(11, 1, -1);
+    SETVERTEX(6, -1, 0, -padOffset);
+    SETVERTEX(7, 1, -1, 0);
+    SETVERTEX(8, 1, 0, -padOffset);
+    SETVERTEX(9, -1, 0, -padOffset);
+    SETVERTEX(10, -1, -1, 0);
+    SETVERTEX(11, 1, -1, 0);
 
 #undef SETVERTEX
 
@@ -103,7 +114,9 @@ bool Init()
     glGenVertexArrays(1, &CompVertexArrayID);
     glBindVertexArray(CompVertexArrayID);
     glEnableVertexAttribArray(0); // position
-    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 2*4, (void*)(0));
+    glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, sizeof(CompVertex), (void*)(offsetof(CompVertex, Position)));
+    glEnableVertexAttribArray(1); // texcoord
+    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(CompVertex), (void*)(offsetof(CompVertex, Texcoord)));
 
     glGenFramebuffers(1, &CompScreenOutputFB);
 
@@ -152,10 +165,13 @@ void SetRenderSettings(RenderSettings& settings)
 
     Scale = scale;
     ScreenW = 256 * scale;
-    ScreenH = 384 * scale;
+    ScreenH = (384+2) * scale;
 
     glBindTexture(GL_TEXTURE_2D, CompScreenOutputTex);
     glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, ScreenW, ScreenH, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+    // fill the padding
+    u8 zeroPixels[ScreenW*2*scale*4] = {0};
+    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 192*scale, ScreenW, 2*scale, GL_RGBA, GL_UNSIGNED_BYTE, zeroPixels);
 
     GLenum fbassign[] = {GL_COLOR_ATTACHMENT0};
     glBindFramebuffer(GL_FRAMEBUFFER, CompScreenOutputFB);
diff --git a/src/GPU_OpenGL_shaders.h b/src/GPU_OpenGL_shaders.h
index 03ddb7a..44be4d0 100644
--- a/src/GPU_OpenGL_shaders.h
+++ b/src/GPU_OpenGL_shaders.h
@@ -22,6 +22,7 @@
 const char* kCompositorVS = R"(#version 140
 
 in vec2 vPosition;
+in vec2 vTexcoord;
 
 smooth out vec2 fTexcoord;
 
@@ -33,7 +34,7 @@ void main()
     fpos.w = 1.0;
 
     gl_Position = fpos;
-    fTexcoord = (vPosition + vec2(1.0, 1.0)) * (vec2(256.0, 384.0) / 2.0);
+    fTexcoord = vTexcoord;
 }
 )";
 
diff --git a/src/frontend/qt_sdl/main.cpp b/src/frontend/qt_sdl/main.cpp
index 8e44bf0..d7821fa 100644
--- a/src/frontend/qt_sdl/main.cpp
+++ b/src/frontend/qt_sdl/main.cpp
@@ -867,22 +867,26 @@ void ScreenPanelGL::initializeGL()
     screenShader->setUniformValue("ScreenTex", (GLint)0);
     screenShader->release();
 
+    // to prevent bleeding between both parts of the screen
+    // with bilinear filtering enabled
+    const int paddedHeight = 192*2+2;
+    const float padPixels = 1.f / paddedHeight;
 
-    float vertices[] =
+    const float vertices[] =
     {
         0,   0,    0, 0,
-        0,   192,  0, 0.5,
-        256, 192,  1, 0.5,
+        0,   192,  0, 0.5 - padPixels,
+        256, 192,  1, 0.5 - padPixels,
         0,   0,    0, 0,
-        256, 192,  1, 0.5,
+        256, 192,  1, 0.5 - padPixels,
         256, 0,    1, 0,
 
-        0,   0,    0, 0.5,
+        0,   0,    0, 0.5 + padPixels,
         0,   192,  0, 1,
         256, 192,  1, 1,
-        0,   0,    0, 0.5,
+        0,   0,    0, 0.5 + padPixels,
         256, 192,  1, 1,
-        256, 0,    1, 0.5
+        256, 0,    1, 0.5 + padPixels
     };
 
     glGenBuffers(1, &screenVertexBuffer);
@@ -903,7 +907,10 @@ void ScreenPanelGL::initializeGL()
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
     glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
-    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 256, 192*2, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 256, paddedHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+    // fill the padding
+    u8 zeroData[256*4*4] = {0};
+    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 192, 256, 2, GL_RGBA, GL_UNSIGNED_BYTE, zeroData);
 
     OSD::Init(this);
 }
@@ -941,7 +948,7 @@ void ScreenPanelGL::paintGL()
         {
             glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 256, 192, GL_RGBA,
                             GL_UNSIGNED_BYTE, GPU::Framebuffer[frontbuf][0]);
-            glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 192, 256, 192, GL_RGBA,
+            glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 192+2, 256, 192, GL_RGBA,
                             GL_UNSIGNED_BYTE, GPU::Framebuffer[frontbuf][1]);
         }
     }