Bug 12357 - Wrong mouse coordinates in mouse events when mouse is captured
Summary: Wrong mouse coordinates in mouse events when mouse is captured
Status: NEW
Alias: None
Product: Class Libraries
Classification: Mono
Component: Windows.Forms ()
Version: master
Hardware: Macintosh Mac OS
: Lowest normal
Target Milestone: Community
Assignee: Bugzilla
Depends on:
Reported: 2013-05-23 04:12 UTC by CO
Modified: 2017-09-01 11:56 UTC (History)
1 user (show)

Tags: mono-community
Is this bug a regression?: ---
Last known good build:

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Description CO 2013-05-23 04:12:27 UTC
When using drop down combos on Mac OS I noticed wrong items being selected when the mouse is outside the drop down list. I tracked this down to wrong mouse coordinates being reported to the combo box. This seems to be the same bug as reported here: https://bugzilla.novell.com/show_bug.cgi?id=557713.

The error likely lies in System.Windows.Forms.CarbonInternal.MouseHandler:

if (client) {
    qdpoint.x = (short) point.x;
    qdpoint.y = (short) point.y;

    Driver.ScreenToClient (hwnd.Handle, ref qdpoint);
} else {
    point.x = qdpoint.x;
    point.y = qdpoint.y;

The first part uses ScreenToClient to convert coordinates which aren't real screen coordinates and basically throws the result away. I think the code should read:

if (client) {
    Driver.ScreenToClient(hwnd.Handle, ref qdpoint);
point.x = qdpoint.x;
point.y = qdpoint.y;