1 files changed, 193 insertions, 0 deletions
diff --git a/src/render/gl_batch.h b/src/render/gl_batch.h
new file mode 100644
index 0000000..944521f
--- /dev/null
+++ b/src/render/gl_batch.h
@@ -0,0 +1,193 @@
+#pragma once
+#include "gl.h"
+
+// this is maybe a bit too much c++ voodoo for my liking
+
+const U32 BATCH_VERTICES_MAX = 16384;
+
+template <typename VERTEX>
+struct GL_BATCH;
+
+// func for setting sampler idx inside of vertex data
+template <typename VERTEX>
+using GL_BATCH_VERTEX_SAMPLER_IDX_FN = void (*)(VERTEX* vertex, U8 idx);
+
+template <typename VERTEX>
+using GL_BATCH_SETUP_FN = void (*)(GL_BATCH<VERTEX>* batch);
+
+template <typename VERTEX>
+struct GL_BATCH_CALL {
+  LIST<VERTEX> vertices{};
+  VEC2 clip_start;
+  VEC2 clip_dim;
+
+  VEC2 viewport_start;
+  VEC2 viewport_dim;
+
+  U16 primitive;
+  LIST<GL_TEX2D*> textures{};
+};
+
+template <typename VERTEX>
+struct GL_BATCH {
+  GL_DATA* gl;
+  GL_SHADER_PROGRAM* shader;
+
+  VEC2 clip_start;
+  VEC2 clip_dim;
+
+  VEC2 viewport_start;
+  VEC2 viewport_dim;
+
+  GLuint vbuffer;
+
+  LIST<GL_BATCH_CALL<VERTEX>> calls{};
+
+  // func for setting up vertex attribs
+  GL_BATCH_SETUP_FN<VERTEX> setup_cb;
+};
+
+/*
+ * takes in a callback func that gets called before the batch is drawn
+ *
+ * should set up vertex attribs correctly according to vertex fmt
+ */
+template <typename VERTEX>
+inline GL_BATCH<VERTEX>* gl_batch_create(
+  GL_DATA* gl,
+  GL_SHADER_PROGRAM* shader,
+  GL_BATCH_SETUP_FN<VERTEX> setup_cb
+) {
+  GL_BATCH<VERTEX>* batch = new GL_BATCH<VERTEX>;
+  batch->gl = gl;
+  batch->shader = shader;
+
+  batch->clip_start = gl->clip_start;
+  batch->clip_dim = gl->clip_dim;
+
+  batch->viewport_start = gl->viewport_start;
+  batch->viewport_dim = gl->viewport_dim;
+
+  batch->setup_cb = setup_cb;
+
+  glGenBuffers( 1, &batch->vbuffer );
+  glBindBuffer( GL_ARRAY_BUFFER, batch->vbuffer );
+  // make sure we have enough vram
+  glBufferData( GL_ARRAY_BUFFER, sizeof( VERTEX ) * BATCH_VERTICES_MAX, 0, GL_DYNAMIC_DRAW );
+  return batch;
+}
+
+template <typename VERTEX>
+inline void gl_batch_destroy( GL_BATCH<VERTEX>* batch ) {
+  glDeleteBuffers( &batch->vbuffer );
+  delete batch;
+}
+
+template <typename VERTEX>
+inline void gl_batch_empty( GL_BATCH<VERTEX>* batch ) {
+  batch->calls.clear();
+}
+
+template <typename VERTEX>
+inline void gl_batch_draw( GL_BATCH<VERTEX>* batch ) {
+  glUseProgram( batch->shader->id );
+
+  VEC2 vp_start, vp_dim, clip_start, clip_dim;
+  gl_get_viewport( batch->gl, &vp_start, &vp_dim );
+  gl_get_clip( batch->gl, &clip_start, &clip_dim );
+
+  batch->setup_cb( batch );
+  batch->calls.each( fn( GL_BATCH_CALL<VERTEX>* call ) {
+    for( U32 i = 0; i < call->textures.size; ++i ) {
+      glActiveTexture( GL_TEXTURE0 + i );
+      glBindTexture( GL_TEXTURE_2D, call->textures.data[i] ? call->textures.data[i]->id : 0 );
+    }
+
+    glBindBuffer( GL_ARRAY_BUFFER, batch->vbuffer );
+    glBufferData(
+      GL_ARRAY_BUFFER,
+      sizeof(VERTEX) * call->vertices.size,
+      call->vertices.data,
+      GL_DYNAMIC_DRAW
+    );
+
+    glBindBuffer( GL_ARRAY_BUFFER, 0 );
+    glDrawArrays( call->primitive, 0, call->vertices.size );
+  } );
+
+  gl_set_viewport( batch->gl, vp_start, vp_dim );
+  gl_set_clip( batch->gl, clip_start, clip_dim );
+}
+
+template <typename VERTEX>
+inline GL_BATCH_CALL<VERTEX>* gl_batch_get_call( GL_BATCH<VERTEX>* batch, GL_TEX2D* tex, U16 primitive, I32* texid ) {
+  U32  n = batch->calls.size;
+  VEC2 vp_start = batch->viewport_start;
+  VEC2 vp_dim = batch->viewport_dim;
+  VEC2 clip_start = batch->clip_start;
+  VEC2 clip_dim = batch->clip_dim;
+
+  if( n ) {
+    GL_BATCH_CALL<VERTEX>* last = &batch->calls.data[n - 1];
+    if( last->primitive == primitive
+     && vp_start == last->clip_start && vp_dim == last->viewport_dim
+     && clip_start == last->clip_start && clip_dim == last->clip_dim
+    ) {
+      I32 idx = last->textures.idx_of( tex );
+      if( idx != -1 ) {
+        *texid = idx;
+        return last;
+      }
+      else if( last->textures.size < batch->gl->shader_texture_limit ) {
+        *texid = last->textures.size;
+        last->textures.push( tex );
+        return last;
+      }
+    }
+  }
+
+
+  GL_BATCH_CALL<VERTEX> call{
+    .vertices = {},
+    .clip_start = batch->clip_start,
+    .clip_dim = batch->clip_dim,
+    .viewport_start = batch->viewport_start,
+    .viewport_dim = batch->viewport_dim,
+    .primitive = primitive,
+    .textures = {},
+  };
+
+  *texid = 0;
+  call.textures.push( tex );
+  return batch->calls.push( call );
+}
+
+template <typename VERTEX>
+inline void gl_batch_insert(
+  GL_BATCH<VERTEX>* batch,
+  VERTEX* vertices,
+  U32 count,
+  GL_TEX2D* tex,
+  U16 primitive = GL_TRIANGLES
+) {
+  if( !count )
+    return;
+
+  GL_BATCH_CALL<VERTEX>* call;
+  I32 texid;
+  VEC2 vp_start, vp_dim;
+  VEC2 clip_start, clip_dim;
+
+  gl_get_viewport( batch->gl, &vp_start, &vp_dim );
+  gl_get_clip( batch->gl, &clip_start, &clip_dim );
+
+  batch->viewport_start = vp_start; batch->viewport_dim = vp_dim;
+  batch->clip_start = clip_start; batch->clip_dim = clip_dim;
+
+  call = gl_batch_get_call( batch, tex, primitive, &texid );
+
+  for( U32 i = 0; i < count; ++i ) {
+    vertices[i].sampler = (!!tex)? texid : SAMPLER_ID_NONE;
+    call->vertices.push( vertices[i] );
+  }
+}