View: provide the transform between different coordinate spaces

There's currently no way for an application to convert between view and
drawing coordinates with a drawing states stack without keeping track of
all the transformations itself, which is not very convenient for helper
or library functions.

Handle other spaces too, for good measure.

Change-Id: Ic8404a1c111e273fff1eebf2f9f59f58246b796c
Reviewed-on: https://review.haiku-os.org/c/haiku/+/5775
Tested-by: Commit checker robot <[email protected]>
Reviewed-by: waddlesplash <[email protected]>

headers/os/interface/View.h

@@ -70,6 +70,16 @@ enum {
 	B_FONT_ALL							= 0x000001FF
 };
 
+typedef enum {
+	B_CURRENT_STATE_COORDINATES,
+	B_PREVIOUS_STATE_COORDINATES,
+	B_VIEW_COORDINATES,
+	B_PARENT_VIEW_DRAW_COORDINATES,
+	B_PARENT_VIEW_COORDINATES,
+	B_WINDOW_COORDINATES,
+	B_SCREEN_COORDINATES
+} coordinate_space;
+
 // view flags
 const uint32 B_FULL_UPDATE_ON_RESIZE	= 0x80000000UL;	/* 31 */
 const uint32 _B_RESERVED1_				= 0x40000000UL;	/* 30 */
@@ -324,6 +334,8 @@ public:
 			void				ScaleBy(double x, double y);
 			void				RotateBy(double angleRadians);
 
+			BAffineTransform	TransformTo(coordinate_space basis) const;
+
 			void				PushState();
 			void				PopState();