[core] Fix overdraw mode on Linux

- Use glBindAttribLocation for GLSL attributes.
- Create a separate shader for each shader that supports overdraw.
  Needed because each uniform location must be known for every program.
- Create a separate VAO for each shader inside buckets.
  Needed because we can only bind a VAO to a specific shader.

Fixes #5435.

1 files changed, 20 insertions, 31 deletions

diff --git a/src/mbgl/shader/shader.cpp b/src/mbgl/shader/shader.cpp
index 80c4c33efc..c9a6b89ade 100644
--- a/src/mbgl/shader/shader.cpp
+++ b/src/mbgl/shader/shader.cpp
@@ -11,10 +11,11 @@
 #include <string>
 #include <fstream>
 #include <cstdio>
+#include <cassert>
 
 namespace mbgl {
 
-Shader::Shader(const char* name_, const char* vertexSource, const char* fragmentSource, gl::ObjectStore& store)
+Shader::Shader(const char* name_, const char* vertexSource, const char* fragmentSource, gl::ObjectStore& store, bool overdraw)
     : name(name_)
     , program(store.createProgram())
     , vertexShader(store.createShader(GL_VERTEX_SHADER))
@@ -27,7 +28,13 @@ Shader::Shader(const char* name_, const char* vertexSource, const char* fragment
         throw util::ShaderException(std::string { "Vertex shader " } + name + " failed to compile");
     }
 
-    if (!compileShader(fragmentShader, fragmentSource)) {
+    std::string fragment(fragmentSource);
+    if (overdraw) {
+        assert(fragment.find("#ifdef OVERDRAW_INSPECTOR") != std::string::npos);
+        fragment.replace(fragment.find_first_of('\n'), 1, "\n#define OVERDRAW_INSPECTOR\n");
+    }
+
+    if (!compileShader(fragmentShader, fragment.c_str())) {
         Log::Error(Event::Shader, "Fragment shader %s failed to compile: %s", name, fragmentSource);
         throw util::ShaderException(std::string { "Fragment shader " } + name + " failed to compile");
     }
@@ -36,39 +43,25 @@ Shader::Shader(const char* name_, const char* vertexSource, const char* fragment
     MBGL_CHECK_ERROR(glAttachShader(program.get(), vertexShader.get()));
     MBGL_CHECK_ERROR(glAttachShader(program.get(), fragmentShader.get()));
 
-    linkProgram(program);
-
-    std::string overdrawSource(fragmentSource);
-    if (overdrawSource.find("#ifdef OVERDRAW_INSPECTOR") != std::string::npos) {
-        programOverdraw = store.createProgram();
-        overdrawShader = store.createShader(GL_FRAGMENT_SHADER);
-
-        overdrawSource.replace(overdrawSource.find_first_of('\n'), 1, "\n#define OVERDRAW_INSPECTOR\n");
-        if (!compileShader(*overdrawShader, overdrawSource.c_str())) {
-            Log::Error(Event::Shader, "Overdraw shader %s failed to compile: %s", name, overdrawSource.c_str());
-            throw util::ShaderException(std::string { "Overdraw shader " } + name + " failed to compile");
-        }
+    // Bind attribute variables
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_pos, "a_pos"));
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_extrude, "a_extrude"));
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_offset, "a_offset"));
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_data, "a_data"));
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_data1, "a_data1"));
+    MBGL_CHECK_ERROR(glBindAttribLocation(program.get(), a_data2, "a_data2"));
 
-        MBGL_CHECK_ERROR(glAttachShader(*programOverdraw, vertexShader.get()));
-        MBGL_CHECK_ERROR(glAttachShader(*programOverdraw, *overdrawShader));
-        linkProgram(*programOverdraw);
-    }
-
-    a_pos = MBGL_CHECK_ERROR(glGetAttribLocation(program.get(), "a_pos"));
-}
-
-void Shader::linkProgram(gl::UniqueProgram& program_) {
     // Link program
     GLint status;
-     MBGL_CHECK_ERROR(glLinkProgram(program_.get()));
+     MBGL_CHECK_ERROR(glLinkProgram(program.get()));
 
-    MBGL_CHECK_ERROR(glGetProgramiv(program_.get(), GL_LINK_STATUS, &status));
+    MBGL_CHECK_ERROR(glGetProgramiv(program.get(), GL_LINK_STATUS, &status));
     if (status == 0) {
         GLint logLength;
-        MBGL_CHECK_ERROR(glGetProgramiv(program_.get(), GL_INFO_LOG_LENGTH, &logLength));
+        MBGL_CHECK_ERROR(glGetProgramiv(program.get(), GL_INFO_LOG_LENGTH, &logLength));
         const auto log = std::make_unique<GLchar[]>(logLength);
         if (logLength > 0) {
-            MBGL_CHECK_ERROR(glGetProgramInfoLog(program_.get(), logLength, &logLength, log.get()));
+            MBGL_CHECK_ERROR(glGetProgramInfoLog(program.get(), logLength, &logLength, log.get()));
             Log::Error(Event::Shader, "Program failed to link: %s", log.get());
         }
         throw util::ShaderException(std::string { "Program " } + name + " failed to link: " + log.get());
@@ -109,10 +102,6 @@ Shader::~Shader() {
         MBGL_CHECK_ERROR(glDetachShader(program.get(), vertexShader.get()));
         MBGL_CHECK_ERROR(glDetachShader(program.get(), fragmentShader.get()));
     }
-    if (programOverdraw) {
-        MBGL_CHECK_ERROR(glDetachShader(*programOverdraw, vertexShader.get()));
-        MBGL_CHECK_ERROR(glDetachShader(*programOverdraw, *overdrawShader));
-    }
 }
 
 } // namespace mbgl