Merge lp:~vanvugt/mir/fix-1339471-demoonly into lp:mir

[Daniel van Vugt]

mir_demo_client_multiwin: Premultiply by alpha to produce correctly
composited colours following changes to the blending equation in r1687.
(LP: #1339471)

[PS Jenkins bot (ps-jenkins)]

PASSED: Continuous integration, rev:1759
http://jenkins.qa.ubuntu.com/job/mir-team-mir-development-branch-ci/2122/
Executed test runs:
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-android-utopic-i386-build/898
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-clang-utopic-amd64-build/904
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-utopic-touch/897
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-team-mir-development-branch-utopic-amd64-ci/643
        deb: http://jenkins.qa.ubuntu.com/job/mir-team-mir-development-branch-utopic-amd64-ci/643/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-team-mir-development-branch-utopic-armhf-ci/641
        deb: http://jenkins.qa.ubuntu.com/job/mir-team-mir-development-branch-utopic-armhf-ci/641/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/generic-mediumtests-builder-utopic-armhf/2863
        deb: http://jenkins.qa.ubuntu.com/job/generic-mediumtests-builder-utopic-armhf/2863/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-mako/2040
    SUCCESS: http://s-jenkins.ubuntu-ci:8080/job/touch-flash-device/9599

Click here to trigger a rebuild:
http://s-jenkins.ubuntu-ci:8080/job/mir-team-mir-development-branch-ci/2122/rebuild

review: Approve (continuous-integration)

[Alexandros Frantzis (afrantzis)]

Looks good.

review: Approve

=== modified file 'examples/multiwin.c'
--- examples/multiwin.c	2014-03-06 06:05:17 +0000
+++ examples/multiwin.c	2014-07-10 08:44:33 +0000
@@ -44,6 +44,13 @@
     }
 }
 
+static void premultiply_alpha(Color *c)
+{
+    c->r = (unsigned)c->r * c->a / 255U;
+    c->g = (unsigned)c->g * c->a / 255U;
+    c->b = (unsigned)c->b * c->a / 255U;
+}
+
 static void put_pixels(void *where, int count, MirPixelFormat format,
                        const Color *color)
 {
@@ -187,6 +194,7 @@
     win[0].fill.g = 0x00;
     win[0].fill.b = 0x00;
     win[0].fill.a = 0x50;
+    premultiply_alpha(&win[0].fill);
 
     parm.name = "green";
     parm.width = 300;
@@ -196,6 +204,7 @@
     win[1].fill.g = 0xff;
     win[1].fill.b = 0x00;
     win[1].fill.a = 0x50;
+    premultiply_alpha(&win[1].fill);
 
     parm.name = "blue";
     parm.width = 150;
@@ -205,6 +214,7 @@
     win[2].fill.g = 0x00;
     win[2].fill.b = 0xff;
     win[2].fill.a = 0x50;
+    premultiply_alpha(&win[2].fill);
 
     signal(SIGINT, shutdown);
     signal(SIGTERM, shutdown);