From 8d9b24b1b84107c90a77d94c86a810cc068fe073 Mon Sep 17 00:00:00 2001
From: dec05eba <dec05eba@protonmail.com>
Date: Wed, 19 Feb 2020 22:14:12 +0100
Subject: Fix rendering of texture with multiple frames

---
 src/RenderBackend/OpenGL/ShaderFrame.cpp | 54 ++++++++++++++++++++++++++++++++
 1 file changed, 54 insertions(+)
 create mode 100644 src/RenderBackend/OpenGL/ShaderFrame.cpp

(limited to 'src/RenderBackend/OpenGL/ShaderFrame.cpp')

diff --git a/src/RenderBackend/OpenGL/ShaderFrame.cpp b/src/RenderBackend/OpenGL/ShaderFrame.cpp
new file mode 100644
index 0000000..3f7ff01
--- /dev/null
+++ b/src/RenderBackend/OpenGL/ShaderFrame.cpp
@@ -0,0 +1,54 @@
+#include "../../../include/RenderBackend/OpenGL/ShaderFrame.hpp"
+#include "../../../include/RenderBackend/OpenGL/opengl.hpp"
+
+namespace amalgine {
+    ShaderFrame::ShaderFrame(u32 shader_program_id) : shader_program_id(shader_program_id), vertex_array_object_id(-1) {
+        glGenVertexArrays(1, &vertex_array_object_id);
+    }
+    
+    ShaderFrame::~ShaderFrame() {
+        glDeleteVertexArrays(1, &vertex_array_object_id);
+    }
+
+    DeviceMemory* ShaderFrame::get_input_by_name(const char *name) {
+        auto it = shader_inputs.find(name);
+        if(it != shader_inputs.end())
+            return it->second.get();
+
+        GLint attrib_location = glGetAttribLocation(shader_program_id, name);
+        if(attrib_location == -1) {
+            fprintf(stderr, "No such attribute in shader: %s\n", name);
+            return nullptr;
+        }
+
+        glBindVertexArray(vertex_array_object_id); // Encapsulate DeviceMemory (vertex buffer object) inside the active vertex array object
+        DeviceMemory *device_memory_ptr = new DeviceMemory(vertex_array_object_id, attrib_location);
+        std::unique_ptr<DeviceMemory> device_memory(device_memory_ptr);
+        device_memory->use();
+        glEnableVertexAttribArray(attrib_location);
+
+        shader_inputs[name] = std::move(device_memory);
+        return device_memory_ptr;
+    }
+
+    Result<Uniform> ShaderFrame::get_uniform_by_name(const char *name) {
+        GLint uniform_id = glGetUniformLocation(shader_program_id, name);
+        if(uniform_id == -1)
+            return Result<Uniform>::Err(std::string("Uniform with name ") + name + " was not found");
+
+        Uniform uniform(uniform_id, shader_program_id);
+        return Result<Uniform>::Ok(std::move(uniform));
+    }
+
+    void ShaderFrame::draw() {
+        glUseProgram(shader_program_id);
+        glBindVertexArray(vertex_array_object_id); // Set the active shader to use the data encapsulated by the vertex array object
+        // TODO: Cache this num_vertices count (and reset it when device memory has changed)
+        int num_vertices = 0;
+        for(const auto &it : shader_inputs) {
+            num_vertices = std::max(num_vertices, it.second->get_num_vertices());
+        }
+        // TODO: Allow specifying mode different than GL_TRIANGLES
+        glDrawArrays(GL_TRIANGLES, 0, num_vertices);
+    }
+}
-- 
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