gles: Fixes for unused VAAs that have no data.

On some drivers having a vertex attribute array enabled with no bound data will cause `GL_INVALID_OPERATION` errors, even though that vertex attribute is not used by the program.

This is a compat workaround for this case where we temporarily disable the vertex attribute array if we believe the program does not use it.

gapis/api/gles/compat.go

@@ -266,6 +266,12 @@ func compat(ctx context.Context, device *device.Instance) (transform.Transformer
 			return
 		}
 
+		if cmd.CmdFlags(ctx, id, s).IsDrawCall() {
+			t := newTweaker(out, dID, cb)
+			disableUnusedAttribArrays(ctx, t)
+			defer t.revert(ctx)
+		}
+
 		switch cmd := cmd.(type) {
 		case *GlBindBuffer:
 			if cmd.Buffer == 0 {
@@ -1289,6 +1295,33 @@ func canUsePrecompiledShader(c *Context, d *device.OpenGLDriver) bool {
 	return c.Constants.Vendor == d.Vendor && c.Constants.Version == d.Version
 }
 
+// disableUnusedAttribArrays disables all vertex attribute arrays that are not
+// used by the currently bound program. This is a compatibility fix for devices
+// that will error with GL_INVALID_OPERATION if there's an enabled (but unused)
+// vertex attribute array that has no array data when drawing. AFAICT, this
+// particular behavior is undefined according to the spec.
+func disableUnusedAttribArrays(ctx context.Context, t *tweaker) {
+	p := t.c.Bound.Program
+	if p == nil || p.ActiveResources == nil {
+		return
+	}
+	inputs := p.ActiveResources.ProgramInputs
+	used := make([]bool, t.c.Constants.MaxVertexAttribBindings)
+	for _, input := range inputs.Range() {
+		for _, l := range input.Locations.Range() {
+			if l >= 0 && l < GLint(len(used)) {
+				used[l] = true
+			}
+		}
+	}
+
+	for l, arr := range t.c.Bound.VertexArray.VertexAttributeArrays.Range() {
+		if arr.Enabled == GLboolean_GL_TRUE && l < AttributeLocation(len(used)) && !used[l] {
+			t.glDisableVertexAttribArray(ctx, l)
+		}
+	}
+}
+
 // It is a no-op to delete objects that do not exist.
 // GAPID uses a shared context for replay - while its fine to delete ids that do
 // not exist in this context, they might exist in another. Strip out any ids

gapis/api/gles/tweaker.go

@@ -91,6 +91,15 @@ func (t *tweaker) glDisable(ctx context.Context, name GLenum) {
 	}
 }
 
+func (t *tweaker) glDisableVertexAttribArray(ctx context.Context, l AttributeLocation) {
+	arr := t.c.Bound.VertexArray.VertexAttributeArrays.Get(l)
+	if arr != nil && arr.Enabled == GLboolean_GL_TRUE {
+		t.doAndUndo(ctx,
+			t.cb.GlDisableVertexAttribArray(l),
+			t.cb.GlEnableVertexAttribArray(l))
+	}
+}
+
 func (t *tweaker) glDepthMask(ctx context.Context, v GLboolean) {
 	if o := t.c.Pixel.DepthWritemask; o != v {
 		t.doAndUndo(ctx,