partially done work on total source tree rework, separation of engine context and game context, generalization of renderer for different backends as well as web platform target

src/rendering/twn_gl_any_rendering.c

@@ -0,0 +1,89 @@
+#include "twn_gl_any_rendering_c.h"
+#include "townengine/context.h"
+#include "townengine/util.h"
+
+#ifdef EMSCRIPTEN
+#include <GLES2/gl2.h>
+#else
+#include <glad/glad.h>
+#endif
+
+
+void setup_viewport(int x, int y, int width, int height) {
+    glViewport(x, y, width, height);
+}
+
+//////// VERTEX BUFFER ////////
+
+vertex_buffer create_vertex_buffer(void) {
+    GLuint result;
+    glGenBuffers(1, &result);
+    return result;
+}
+
+
+void delete_vertex_buffer(vertex_buffer buffer) {
+    glDeleteBuffers(1, &buffer);
+}
+
+
+void specify_vertex_buffer(vertex_buffer buffer, void *data, size_t bytes) {
+    glBindBuffer(GL_ARRAY_BUFFER, buffer);
+    glBufferData(GL_ARRAY_BUFFER, bytes, data, GL_STREAM_DRAW);
+}
+
+//////// END OF VERTEX BUFFER ////////
+
+
+void bind_quad_element_buffer(void) {
+    static GLuint buffer = 0;
+
+    /* it's only generated once at runtime */
+    if (buffer == 0) {
+        glGenBuffers(1, &buffer);
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffer);
+        glBufferData(GL_ELEMENT_ARRAY_BUFFER,
+                     QUAD_ELEMENT_BUFFER_LENGTH * 6 * sizeof(uint16_t),
+                     NULL,
+                     GL_STATIC_DRAW);
+
+        uint16_t *const indices = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER,
+                                              GL_WRITE_ONLY);
+        if (!indices)
+            CRY("Quad indices generation", "glMapBuffer() failed");
+
+        for (uint16_t i = 0; i < QUAD_ELEMENT_BUFFER_LENGTH; ++i) {
+            indices[i * 6 + 0] = (uint16_t)(i * 4 + 0);
+            indices[i * 6 + 1] = (uint16_t)(i * 4 + 1);
+            indices[i * 6 + 2] = (uint16_t)(i * 4 + 2);
+            indices[i * 6 + 3] = (uint16_t)(i * 4 + 2);
+            indices[i * 6 + 4] = (uint16_t)(i * 4 + 3);
+            indices[i * 6 + 5] = (uint16_t)(i * 4 + 0);
+        }
+
+        glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);
+
+    } else
+        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, buffer);
+}
+
+
+void clear_draw_buffer(void) {
+    glClearColor((1.0f / 255) * 230,
+                 (1.0f / 255) * 230,
+                 (1.0f / 255) * 230, 1);
+
+    glClear(GL_COLOR_BUFFER_BIT |
+            GL_DEPTH_BUFFER_BIT |
+            GL_STENCIL_BUFFER_BIT);
+}
+
+
+void swap_buffers(void) {
+    SDL_GL_SwapWindow(ctx.window);
+}
+
+
+void set_depth_range(double low, double high) {
+    glDepthRange(low, high);
+}