Fixing scissoring

src/platform/render_opengl.cpp

@@ -14,7 +14,8 @@ struct Vertex2D {
 struct VertexNode2D {
     VertexNode2D *next;
     int           count;
-    Vertex2D      vertices[1024 * 64];
+    Vertex2D      vertices[1024 * 16];
+    Rect2         scissor;
 };
 
 struct VertexList2D {
@@ -29,17 +30,27 @@ unsigned VBO, VAO;
 Shader   Shader2D;
 Arena    RenderArena;
 Vec2     WindowSize;
+Rect2    CurrentScissor;
 
 Font MainFont;
 Int  FontLineSpacing;
 Int  FontCharSpacing;
 
-void BeginFrameRender(Vec2 window_size) {
+Rect2 GetScreenRectF() {
+    Rect2 result = {0, 0, WindowSize.x, WindowSize.y};
+    return result;
+}
+
+Rect2I GetScreenRectI() {
+    Rect2I result = {0, 0, (Int)WindowSize.x, (Int)WindowSize.y};
+    return result;
+}
+void BeginFrameRender() {
     Clear(&RenderArena);
     TotalVertexCount = 0;
     Vertices.first   = NULL;
     Vertices.last    = NULL;
-    WindowSize       = window_size;
+    CurrentScissor   = GetScreenRectF();
 }
 
 void EndFrameRender(Color color) {
@@ -50,8 +61,9 @@ void EndFrameRender(Color color) {
     glDisable(GL_CULL_FACE);
 
     glViewport(0, 0, (GLsizei)WindowSize.x, (GLsizei)WindowSize.y);
+    glScissor(0, 0, (GLsizei)WindowSize.x, (GLsizei)WindowSize.y);
     glClearColor(color.r, color.g, color.b, color.a);
-    glClear(GL_COLOR_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);
+    glClear(GL_COLOR_BUFFER_BIT);
 
     // Default draw using the font texture
     glBindProgramPipeline(Shader2D.pipeline);
@@ -59,6 +71,12 @@ void EndFrameRender(Color color) {
     float yinverse = 1.f / (WindowSize.y / 2.f);
     glProgramUniform2f(Shader2D.vshader, 0, xinverse, yinverse);
     for (VertexNode2D *it = Vertices.first; it; it = it->next) {
+        Rect2   rect = it->scissor;
+        GLint   x    = (GLint)rect.min.x;
+        GLint   y    = (GLint)rect.min.y;
+        GLsizei w    = (GLsizei)(rect.max.x - rect.min.x);
+        GLsizei h    = (GLsizei)(rect.max.y - rect.min.y);
+        glScissor(x, (GLint)WindowSize.y - h, w, h);
         glNamedBufferSubData(VBO, 0, it->count * sizeof(Vertex2D), it->vertices);
         glBindVertexArray(VAO);
         GLint s_texture = 0; // texture unit that sampler2D will use in GLSL code
@@ -183,11 +201,39 @@ Shader CreateShader(char *glsl_vshader, char *glsl_fshader) {
     } while (0)
 #define SLL_QUEUE_ADD(f, l, n) SLL_QUEUE_ADD_MOD(f, l, n, next)
 
+VertexNode2D *AllocVertexNode2D(Allocator allocator, VertexList2D *list) {
+    VertexNode2D *node = AllocType(allocator, VertexNode2D);
+    SLL_QUEUE_ADD(list->first, list->last, node);
+    return node;
+}
+
+void SetScissor(Rect2 rect) {
+    CurrentScissor = rect;
+
+    VertexNode2D *node = Vertices.last;
+    if (!node) {
+        node          = AllocVertexNode2D(RenderArena, &Vertices);
+        node->scissor = rect;
+        return;
+    }
+
+    if (node->scissor != rect && node->count == 0) {
+        node->scissor = rect;
+        return;
+    }
+
+    if (node->scissor != rect) {
+        node          = AllocVertexNode2D(RenderArena, &Vertices);
+        node->scissor = rect;
+        return;
+    }
+}
+
 Vertex2D *AllocVertex2D(Allocator allocator, VertexList2D *list, int count) {
     VertexNode2D *node = list->last;
     if (node == 0 || node->count + count > Lengthof(node->vertices)) {
-        node = AllocType(allocator, VertexNode2D);
-        SLL_QUEUE_ADD(list->first, list->last, node);
+        node          = AllocVertexNode2D(allocator, list);
+        node->scissor = CurrentScissor;
     }
 
     TotalVertexCount += count;
@@ -249,7 +295,7 @@ void DrawRect(Rect2 rect, Color color) {
 }
 
 Vec2 DrawString(Font *font, String16 string, Vec2 pos, Color color, bool draw = true) {
-    pos.y += font->ascent;
+    pos.y += font->ascent - font->descent;
     Vec2 original_pos = pos;
     For(string) {
         Glyph *g    = GetGlyph(font, it);
@@ -277,25 +323,3 @@ Int GetLineSpacing(Font *font) {
     Int result = (Int)(font->ascent - font->descent + font->line_gap);
     return result;
 }
-
-void BeginScissor(Rect2 rect) {
-    glScissor((GLint)rect.min.x, (GLint)rect.min.y, (GLsizei)(rect.max.x - rect.min.x), (GLsizei)(rect.max.y - rect.min.y));
-}
-
-void BeginScissor(Rect2I rect) {
-    glScissor((GLint)rect.min.x, (GLint)rect.min.y, (GLsizei)(rect.max.x - rect.min.x), (GLsizei)(rect.max.y - rect.min.y));
-}
-
-void EndScissor() {
-    glScissor(0, 0, (GLsizei)WindowSize.x, (GLsizei)WindowSize.y);
-}
-
-Rect2 GetScreenRectF() {
-    Rect2 result = {0, 0, WindowSize.x, WindowSize.y};
-    return result;
-}
-
-Rect2I GetScreenRectI() {
-    Rect2I result = {0, 0, (Int)WindowSize.x, (Int)WindowSize.y};
-    return result;
-}