- /* _NEW_VIEWPORT */
- vp->viewport.m00 = v[MAT_SX];
- vp->viewport.m11 = v[MAT_SY] * y_scale;
- vp->viewport.m22 = v[MAT_SZ] * depth_scale;
- vp->viewport.m30 = v[MAT_TX];
- vp->viewport.m31 = v[MAT_TY] * y_scale + y_bias;
- vp->viewport.m32 = v[MAT_TZ] * depth_scale;
+ for (unsigned i = 0; i < ctx->Const.MaxViewports; i++) {
+ float scale[3], translate[3];
+ _mesa_get_viewport_xform(ctx, i, scale, translate);
+
+ /* According to the "Vertex X,Y Clamping and Quantization" section of
+ * the Strips and Fans documentation, objects must not have a
+ * screen-space extents of over 8192 pixels, or they may be
+ * mis-rasterized. The maximum screen space coordinates of a small
+ * object may larger, but we have no way to enforce the object size
+ * other than through clipping.
+ *
+ * If you're surprised that we set clip to -gbx to +gbx and it seems
+ * like we'll end up with 16384 wide, note that for a 8192-wide render
+ * target, we'll end up with a normal (-1, 1) clip volume that just
+ * covers the drawable.
+ */
+ const float maximum_guardband_extent = 8192;
+ const float gbx = maximum_guardband_extent / ctx->ViewportArray[i].Width;
+ const float gby = maximum_guardband_extent / ctx->ViewportArray[i].Height;
+
+ vp[i].guardband.xmin = -gbx;
+ vp[i].guardband.xmax = gbx;
+ vp[i].guardband.ymin = -gby;
+ vp[i].guardband.ymax = gby;
+
+ /* _NEW_VIEWPORT */
+ vp[i].viewport.m00 = scale[0];
+ vp[i].viewport.m11 = scale[1] * y_scale;
+ vp[i].viewport.m22 = scale[2];
+ vp[i].viewport.m30 = translate[0];
+ vp[i].viewport.m31 = translate[1] * y_scale + y_bias;
+ vp[i].viewport.m32 = translate[2];
+ }