gm: add a flag to force perspective usage in all gms

gm/gm.h

Index: gm/gm.h
diff --git a/gm/gm.h b/gm/gm.h
index 3a651607414372639cea46cc6cb5472a08f4a0a7..239b219d4589380077ef8af8ee8b0cf71217b7ba 100644
--- a/gm/gm.h
+++ b/gm/gm.h
@@ -11,6 +11,7 @@
 #include "SkBitmap.h"
 #include "SkBitmapDevice.h"
 #include "SkCanvas.h"
+#include "SkCommandLineFlags.h"
 #include "SkPaint.h"
 #include "SkSize.h"
 #include "SkString.h"
@@ -20,6 +21,8 @@
 #include "GrContext.h"
 #endif
 
+DECLARE_bool(forcePerspectiveMatrix);
+
 #define DEF_GM(code) \
     static skiagm::GM*          SK_MACRO_APPEND_LINE(F_)(void*) { code; } \
     static skiagm::GMRegistry   SK_MACRO_APPEND_LINE(R_)(SK_MACRO_APPEND_LINE(F_));
@@ -74,6 +77,13 @@ namespace skiagm {
         // Most GMs will return the identity matrix, but some PDFs tests
         // require setting the initial transform.
         SkMatrix getInitialTransform() const {

[reed1, 2013/09/23 18:48:40]

I think we could generalize this guy a little for this CL:

1. I think you should concat w/ onGetInitialTransform(), instead of either/or
2. Perhaps gm itself has a setter (which gmmain.cpp can call) that accepts an
initial matrix.

#2 means you don't need to know about any flags here, just a matrix data blob in
the base-class of gm. THen the code would be something like

SkMatrix getInitialMatrix() const {
    SkMatrix matrix = fStarterMatrix;   // identity or set by the new
setStarterMatrix(...) on base class
    matrix.preConcat(this->onGetInitialTransform());
    return matrix;
}

[edisonn, 2013/09/23 19:38:04]

Done.

+            if (FLAGS_forcePerspectiveMatrix) {
+                SkMatrix perspective;
+                perspective.setIdentity();
+                perspective.setPerspY(SkScalarDiv(SK_Scalar1, SkIntToScalar(1000)));
+                perspective.setSkewX(SkScalarDiv(SkIntToScalar(8), SkIntToScalar(25)));
+                return perspective;
+            }
             return this->onGetInitialTransform();
         }