draw: implement support for multiple viewports

This adds support for multiple viewports to the draw module.
Multiple viewports depend on the presence of geometry shaders
which can write the viewport index.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: José Fonseca<jfonseca@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>

1 files changed, 42 insertions, 10 deletions

diff --git a/src/gallium/auxiliary/draw/draw_context.c b/src/gallium/auxiliary/draw/draw_context.c
index b555c65e85..4250f10d13 100644
--- a/src/gallium/auxiliary/draw/draw_context.c
+++ b/src/gallium/auxiliary/draw/draw_context.c
@@ -318,17 +318,24 @@ void draw_set_viewport_states( struct draw_context *draw,
 {
    const struct pipe_viewport_state *viewport = vps;
    draw_do_flush(draw, DRAW_FLUSH_PARAMETER_CHANGE);
-   draw->viewport = *viewport; /* struct copy */
-   draw->identity_viewport = (viewport->scale[0] == 1.0f &&
-                              viewport->scale[1] == 1.0f &&
-                              viewport->scale[2] == 1.0f &&
-                              viewport->scale[3] == 1.0f &&
-                              viewport->translate[0] == 0.0f &&
-                              viewport->translate[1] == 0.0f &&
-                              viewport->translate[2] == 0.0f &&
-                              viewport->translate[3] == 0.0f);
 
-   draw_vs_set_viewport( draw, viewport );
+   if (start_slot > PIPE_MAX_VIEWPORTS)
+      return;
+
+   if ((start_slot + num_viewports) > PIPE_MAX_VIEWPORTS)
+      num_viewports = PIPE_MAX_VIEWPORTS - start_slot;
+
+   memcpy(draw->viewports + start_slot, vps,
+          sizeof(struct pipe_viewport_state) * num_viewports);
+   draw->identity_viewport = (num_viewports == 1) &&
+      (viewport->scale[0] == 1.0f &&
+       viewport->scale[1] == 1.0f &&
+       viewport->scale[2] == 1.0f &&
+       viewport->scale[3] == 1.0f &&
+       viewport->translate[0] == 0.0f &&
+       viewport->translate[1] == 0.0f &&
+       viewport->translate[2] == 0.0f &&
+       viewport->translate[3] == 0.0f);
 }
 
 
@@ -695,6 +702,31 @@ draw_current_shader_position_output(const struct draw_context *draw)
 
 /**
  * Return the index of the shader output which will contain the
+ * viewport index.
+ */
+uint
+draw_current_shader_viewport_index_output(const struct draw_context *draw)
+{
+   if (draw->gs.geometry_shader)
+      return draw->gs.geometry_shader->viewport_index_output;
+   return 0;
+}
+
+/**
+ * Returns true if there's a geometry shader bound and the geometry
+ * shader writes out a viewport index.
+ */
+boolean
+draw_current_shader_uses_viewport_index(const struct draw_context *draw)
+{
+   if (draw->gs.geometry_shader)
+      return draw->gs.geometry_shader->info.writes_viewport_index;
+   return FALSE;
+}
+
+
+/**
+ * Return the index of the shader output which will contain the
  * vertex position.
  */
 uint