d2d1: Add the ID2D1GradientStopCollection interface.

include/d2d1.idl

@@ -191,6 +191,13 @@ typedef enum D2D1_BITMAP_INTERPOLATION_MODE
     D2D1_BITMAP_INTERPOLATION_MODE_FORCE_DWORD = 0xffffffff,
 } D2D1_BITMAP_INTERPOLATION_MODE;
 
+typedef enum D2D1_GAMMA
+{
+    D2D1_GAMMA_2_2 = 0,
+    D2D1_GAMMA_1_0 = 1,
+    D2D1_GAMMA_FORCE_DWORD = 0xffffffff,
+} D2D1_GAMMA;
+
 typedef struct D2D1_BEZIER_SEGMENT
 {
     D2D1_POINT_2F point1;
@@ -248,6 +255,12 @@ typedef struct D2D1_DRAWING_STATE_DESCRIPTION
     D2D1_MATRIX_3X2_F transform;
 } D2D1_DRAWING_STATE_DESCRIPTION;
 
+typedef struct D2D1_GRADIENT_STOP
+{
+    float position;
+    D2D1_COLOR_F color;
+} D2D1_GRADIENT_STOP;
+
 [
     local,
     object,
@@ -630,5 +643,21 @@ interface ID2D1SolidColorBrush : ID2D1Brush
     D2D1_COLOR_F GetColor();
 }
 
+[
+    local,
+    object,
+    uuid(2cd906a7-12e2-11dc-9fed-001143a055f9)
+]
+interface ID2D1GradientStopCollection : ID2D1Resource
+{
+    UINT32 GetGradientStopCount();
+    void GetGradientStops(
+        [out] D2D1_GRADIENT_STOP *stops,
+        [in] UINT32 stop_count
+    );
+    D2D1_GAMMA GetColorInterpolationGamma();
+    D2D1_EXTEND_MODE GetExtendMode();
+}
+
 [local] HRESULT __stdcall D2D1CreateFactory(D2D1_FACTORY_TYPE factory_type, REFIID iid,
         const D2D1_FACTORY_OPTIONS *factory_options, void **factory);