Implement support for GL_ARB_draw_buffers with GL_MAX_DRAW_BUFFERS > 1.

GL_MAX_DRAW_BUFFERS is currently 4.
Added gl_FragData[] output for fragment programs.
In _swrast_write_rgba_span() loop over the color outputs/renderbuffers.

1 files changed, 21 insertions, 3 deletions

diff --git a/src/mesa/swrast/s_fragprog.c b/src/mesa/swrast/s_fragprog.c
index dbfc1b8c0c..7260759306 100644
--- a/src/mesa/swrast/s_fragprog.c
+++ b/src/mesa/swrast/s_fragprog.c
@@ -139,7 +139,9 @@ init_machine(GLcontext *ctx, struct gl_program_machine *machine,
 static void
 run_program(GLcontext *ctx, SWspan *span, GLuint start, GLuint end)
 {
+   SWcontext *swrast = SWRAST_CONTEXT(ctx);
    const struct gl_fragment_program *program = ctx->FragmentProgram._Current;
+   const GLbitfield outputsWritten = program->Base.OutputsWritten;
    struct gl_program_machine machine;
    GLuint i;
 
@@ -148,12 +150,28 @@ run_program(GLcontext *ctx, SWspan *span, GLuint start, GLuint end)
          init_machine(ctx, &machine, program, span, i);
 
          if (_mesa_execute_program(ctx, &program->Base, &machine)) {
+
             /* Store result color */
-            COPY_4V(span->array->attribs[FRAG_ATTRIB_COL0][i],
-                    machine.Outputs[FRAG_RESULT_COLR]);
+            if (outputsWritten & (1 << FRAG_RESULT_COLR)) {
+               COPY_4V(span->array->attribs[FRAG_ATTRIB_COL0][i],
+                       machine.Outputs[FRAG_RESULT_COLR]);
+            }
+            else {
+               /* Multiple drawbuffers / render targets
+                * Note that colors beyond 0 and 1 will overwrite other
+                * attributes, such as FOGC, TEX0, TEX1, etc.  That's OK.
+                */
+               GLuint output;
+               for (output = 0; output < swrast->_NumColorOutputs; output++) {
+                  if (outputsWritten & (1 << (FRAG_RESULT_DATA0 + output))) {
+                     COPY_4V(span->array->attribs[FRAG_ATTRIB_COL0+output][i],
+                             machine.Outputs[FRAG_RESULT_DATA0 + output]);
+                  }
+               }
+            }
 
             /* Store result depth/z */
-            if (program->Base.OutputsWritten & (1 << FRAG_RESULT_DEPR)) {
+            if (outputsWritten & (1 << FRAG_RESULT_DEPR)) {
                const GLfloat depth = machine.Outputs[FRAG_RESULT_DEPR][2];
                if (depth <= 0.0)
                   span->array->z[i] = 0;