kc3-lang/SDL

diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
index c38ee97..2df9d54 100644
--- a/src/render/opengles2/SDL_render_gles2.c
+++ b/src/render/opengles2/SDL_render_gles2.c
@@ -28,6 +28,16 @@
 #include "../../video/SDL_blit.h"
 #include "SDL_shaders_gles2.h"
 
+/* WebGL doesn't offer client-side arrays, so use Vertex Buffer Objects
+   on Emscripten, which converts GLES2 into WebGL calls.
+   In all other cases, attempt to use client-side arrays, as they tend to
+   be faster. */
+#if defined(__EMSCRIPTEN__)
+#define USE_VERTEX_BUFFER_OBJECTS 1
+#else
+#define USE_VERTEX_BUFFER_OBJECTS 0
+#endif
+
 /* To prevent unnecessary window recreation,
  * these should match the defaults selected in SDL_GL_ResetAttributes
  */
@@ -151,9 +161,12 @@ typedef struct GLES2_RenderData
     GLES2_ProgramCache program_cache;
     Uint8 clear_r, clear_g, clear_b, clear_a;
 
+#if USE_VERTEX_BUFFER_OBJECTS
     GLuint vertex_buffers[8];
     size_t vertex_buffer_size[8];
     int current_vertex_buffer;
+#endif
+
     GLES2_DrawStateCache drawstate;
 } GLES2_RenderData;
 
@@ -844,7 +857,7 @@ GLES2_QueueGeometry(SDL_Renderer *renderer, SDL_RenderCommand *cmd, SDL_Texture 
 }
 
 static int
-SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, const GLES2_ImageSource imgsrc)
+SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, const GLES2_ImageSource imgsrc, void *vertices)
 {
     SDL_Texture *texture = cmd->data.draw.texture;
     const SDL_BlendMode blend = cmd->data.draw.blend;
@@ -926,7 +939,7 @@ SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, const GLES2_I
     }
 
     if (texture) {
-        SDL_Vertex *verts = (SDL_Vertex *) (cmd->data.draw.first);
+        SDL_Vertex *verts = (SDL_Vertex *) (((Uint8 *) vertices) + cmd->data.draw.first);
         data->glVertexAttribPointer(GLES2_ATTRIBUTE_TEXCOORD, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *)&verts->tex_coord);
     }
 
@@ -960,7 +973,7 @@ SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, const GLES2_I
 
     /* all drawing commands use this */
     {
-        SDL_VertexSolid *verts = (SDL_VertexSolid *) (cmd->data.draw.first);
+        SDL_VertexSolid *verts = (SDL_VertexSolid *) (((Uint8 *) vertices) + cmd->data.draw.first);
         data->glVertexAttribPointer(GLES2_ATTRIBUTE_POSITION, 2, GL_FLOAT, GL_FALSE, stride, (const GLvoid *) &verts->position);
         data->glVertexAttribPointer(GLES2_ATTRIBUTE_COLOR, 4, GL_UNSIGNED_BYTE, GL_TRUE /* Normalized */, stride, (const GLvoid *) &verts->color);
     }
@@ -969,7 +982,7 @@ SetDrawState(GLES2_RenderData *data, const SDL_RenderCommand *cmd, const GLES2_I
 }
 
 static int
-SetCopyState(SDL_Renderer *renderer, const SDL_RenderCommand *cmd)
+SetCopyState(SDL_Renderer *renderer, const SDL_RenderCommand *cmd, void *vertices)
 {
     GLES2_RenderData *data = (GLES2_RenderData *) renderer->driverdata;
     GLES2_ImageSource sourceType = GLES2_IMAGESOURCE_TEXTURE_ABGR;
@@ -1079,7 +1092,7 @@ SetCopyState(SDL_Renderer *renderer, const SDL_RenderCommand *cmd)
         }
     }
 
-    return SetDrawState(data, cmd, sourceType);
+    return SetDrawState(data, cmd, sourceType, vertices);
 }
 
 static int
@@ -1087,8 +1100,11 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
 {
     GLES2_RenderData *data = (GLES2_RenderData *) renderer->driverdata;
     const SDL_bool colorswap = (renderer->target && (renderer->target->format == SDL_PIXELFORMAT_ARGB8888 || renderer->target->format == SDL_PIXELFORMAT_RGB888));
+
+#if USE_VERTEX_BUFFER_OBJECTS
     const int vboidx = data->current_vertex_buffer;
     const GLuint vbo = data->vertex_buffers[vboidx];
+#endif
 
     if (GLES2_ActivateRenderer(renderer) < 0) {
         return -1;
@@ -1106,6 +1122,7 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
         }
     }
 
+#if USE_VERTEX_BUFFER_OBJECTS
     /* upload the new VBO data for this set of commands. */
     data->glBindBuffer(GL_ARRAY_BUFFER, vbo);
     if (data->vertex_buffer_size[vboidx] < vertsize) {
@@ -1120,6 +1137,8 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
     if (data->current_vertex_buffer >= SDL_arraysize(data->vertex_buffers)) {
         data->current_vertex_buffer = 0;
     }
+    vertices = NULL;  /* attrib pointers will be offsets into the VBO. */
+#endif
 
     while (cmd) {
         switch (cmd->command) {
@@ -1184,7 +1203,7 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
                 break;
 
             case SDL_RENDERCMD_DRAW_LINES: {
-                if (SetDrawState(data, cmd, GLES2_IMAGESOURCE_SOLID) == 0) {
+                if (SetDrawState(data, cmd, GLES2_IMAGESOURCE_SOLID, vertices) == 0) {
                     size_t count = cmd->data.draw.count;
                     if (count > 2) {
                         /* joined lines cannot be grouped */
@@ -1242,9 +1261,9 @@ GLES2_RunCommandQueue(SDL_Renderer * renderer, SDL_RenderCommand *cmd, void *ver
                 }
 
                 if (thistexture) {
-                    ret = SetCopyState(renderer, cmd);
+                    ret = SetCopyState(renderer, cmd, vertices);
                 } else {
-                    ret = SetDrawState(data, cmd, GLES2_IMAGESOURCE_SOLID);
+                    ret = SetDrawState(data, cmd, GLES2_IMAGESOURCE_SOLID, vertices);
                 }
 
                 if (ret == 0) {
@@ -1308,8 +1327,10 @@ GLES2_DestroyRenderer(SDL_Renderer *renderer)
                 data->framebuffers = nextnode;
             }
 
+#if USE_VERTEX_BUFFER_OBJECTS
             data->glDeleteBuffers(SDL_arraysize(data->vertex_buffers), data->vertex_buffers);
             GL_CheckError("", renderer);
+#endif
 
             SDL_GL_DeleteContext(data->context);
         }
@@ -2071,8 +2092,10 @@ GLES2_CreateRenderer(SDL_Window *window, Uint32 flags)
     data->glGetIntegerv(GL_MAX_TEXTURE_SIZE, &value);
     renderer->info.max_texture_height = value;
 
+#if USE_VERTEX_BUFFER_OBJECTS
     /* we keep a few of these and cycle through them, so data can live for a few frames. */
     data->glGenBuffers(SDL_arraysize(data->vertex_buffers), data->vertex_buffers);
+#endif
 
     data->framebuffers = NULL;
     data->glGetIntegerv(GL_FRAMEBUFFER_BINDING, &window_framebuffer);