Merge lp:~vanvugt/mir/workaround-1522673 into lp:mir

[Daniel van Vugt]

Work around unpredictable scroll magnitude. (LP: #1522673)

Knowing that all desktop mice implement scroll wheel as discrete
button 4/5 events, a robust client should do this anyway. The existence
of a magnitude is an illusion introduced by libinput, so ignore it.

The direction is still backwards but we'll fix that in one of the
"fix" branches.

I still wonder why input APIs insist on creating this problem with
a scroll "axis". All wheel mice I've ever seen emitted discrete
button events. It would be clearer for everyone if we just kept the button
4/5 events. In Xmir I actually have to synthesise button 4/5 events from the vscroll information anyway.

[PS Jenkins bot (ps-jenkins)]

PASSED: Continuous integration, rev:3179
http://jenkins.qa.ubuntu.com/job/mir-ci/5782/
Executed test runs:
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-android-vivid-i386-build/5213
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-clang-vivid-amd64-build/4119
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-vivid-touch/5162
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-xenial-touch/110/console
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-xenial-amd64-ci/112
        deb: http://jenkins.qa.ubuntu.com/job/mir-xenial-amd64-ci/112/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-xenial-i386-ci/111
        deb: http://jenkins.qa.ubuntu.com/job/mir-xenial-i386-ci/111/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/5161
        deb: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-vivid-armhf/5161/artifact/work/output/*zip*/output.zip
    SUCCESS: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-runner-touch/7691
    SUCCESS: http://s-jenkins.ubuntu-ci:8080/job/touch-flash-device/25832
    FAILURE: http://jenkins.qa.ubuntu.com/job/mir-mediumtests-builder-xenial-armhf/108/console

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review: Approve (continuous-integration)

[Alan Griffiths (alan-griffiths)]

OK

review: Approve

=== modified file 'playground/demo-shell/window_manager.cpp'
--- playground/demo-shell/window_manager.cpp	2015-08-07 05:46:34 +0000
+++ playground/demo-shell/window_manager.cpp	2015-12-07 08:43:59 +0000
@@ -387,10 +387,11 @@
 
     float new_zoom_mag = 0.0f;  // zero means unchanged
 
-   if (modifiers & mir_input_event_modifier_meta &&
-       action == mir_pointer_action_motion)
-   {
-        zoom_exponent += vscroll;
+    if (modifiers & mir_input_event_modifier_meta &&
+        action == mir_pointer_action_motion &&
+        vscroll != 0.0f)
+    {
+        zoom_exponent += vscroll > 0.0f ? 1.0f : -1.0f;
 
         // Negative exponents do work too, but disable them until
         // there's a clear edge to the desktop.
@@ -449,7 +450,7 @@
         vscroll)
     {
         float alpha = surf->alpha();
-        alpha += 0.1f * vscroll;
+        alpha += vscroll > 0.0f ? 0.1f : -0.1f;
         if (alpha < 0.0f)
             alpha = 0.0f;
         else if (alpha > 1.0f)