Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit b5c17a64 authored by Mike Reed's avatar Mike Reed
Browse files

experimental fix for compatibility mode. When we scale up by 1.5 (240 dpi), we... 

experimental fix for compatibility mode. When we scale up by 1.5 (240 dpi), we put stretched ninepatches on
exact pixel boundaries when we walk the inverse matrix (e.g. 2/3, 1+1/3, 2, 2+2/3, 3+1/3, 4, ...).

These are not stable, since any variance in the inverse matrix (even in the lowest bit) can cause some other
part of the ninepatch to start a hair to the left, resulting in misaligning every 3 pixels.

The fix changes the matrix' phase enough to keep all of the stretched ninepatches in phase.
parent 77fa24a5

core/java/android/content/res/CompatibilityInfo.java

+19 −0
Original line number Diff line number Diff line
@@ -274,6 +274,25 @@ public class CompatibilityInfo { 
         * Apply translation to the canvas that is necessary to draw the content.

         */

        public void translateCanvas(Canvas canvas) {

            if (applicationScale == 1.5f) {

                /*  When we scale for compatibility, we can put our stretched

                    bitmaps and ninepatches on exacty 1/2 pixel boundaries,

                    which can give us inconsistent drawing due to imperfect

                    float precision in the graphics engine's inverse matrix.

                 

                    As a work-around, we translate by a tiny amount to avoid

                    landing on exact pixel centers and boundaries, giving us

                    the slop we need to draw consistently.

                 

                    This constant is meant to resolve to 1/255 after it is

                    scaled by 1.5 (applicationScale). Note, this is just a guess

                    as to what is small enough not to create its own artifacts,

                    and big enough to avoid the precision problems. Feel free

                    to experiment with smaller values as you choose.

                 */

                final float tinyOffset = 2.0f / (3 * 255);

                canvas.translate(tinyOffset, tinyOffset);

            }

            canvas.scale(applicationScale, applicationScale);

        }