tdf#156679 wina11y: Convert screen to local coords as needed

When `AccTextBase::get_offsetAtPoint` gets called with
screen coordinates, convert them to local coordinates
within the text object first, because that is what
`XAccessibleText::getIndexAtPoint` expects.

Not doing so resulted in NVDA failing to create
a TextInfo object in the mouse event handler [1]
when hovering over a Calc cell containing text,
because the method would always return an offset
of -1.

With this change in place, NVDA now announces the
text when hovering over the text and mouse tracking
is enabled in NVDA (which is the case by default).
Other than with Microsoft Excel, the text is only
announced when the mouse is actually over the text,
not over free space in the cell, which might be
because Excel uses UIA and the UIA equivalent,
`ITextProvider::RangeFromPoint` [2] shall also return
the index of the closest character when the point
itself is not over the actual bounds of any
character.

[1] https://github.com/nvaccess/nvda/blob/a198c9b5f27e47ff2830f77c833eec584078dfd8/source/NVDAObjects/__init__.py#L1209
[2] https://learn.microsoft.com/en-us/windows/win32/api/uiautomationcore/nf-uiautomationcore-itextprovider-rangefrompoint

Change-Id: I1e4ab2dd3dace5fea1de2eef67a91fe3c31218a9
Reviewed-on: https://gerrit.libreoffice.org/c/core/+/155492
Tested-by: Jenkins
Reviewed-by: Michael Weghorn <m.weghorn@posteo.de>

1 files changed, 15 insertions, 1 deletions

diff --git a/winaccessibility/source/UAccCOM/AccTextBase.cxx b/winaccessibility/source/UAccCOM/AccTextBase.cxx
index 183ec3467655..b70b13c0a980 100644
--- a/winaccessibility/source/UAccCOM/AccTextBase.cxx
+++ b/winaccessibility/source/UAccCOM/AccTextBase.cxx
@@ -417,7 +417,7 @@ COM_DECLSPEC_NOTHROW STDMETHODIMP CAccTextBase::get_nSelections(long * nSelectio
    * @param offset Variant to accept offset.
    * @return Result.
 */
-COM_DECLSPEC_NOTHROW STDMETHODIMP CAccTextBase::get_offsetAtPoint(long x, long y, IA2CoordinateType, long * offset)
+COM_DECLSPEC_NOTHROW STDMETHODIMP CAccTextBase::get_offsetAtPoint(long x, long y, IA2CoordinateType coordType, long * offset)
 {
     SolarMutexGuard g;
 
@@ -432,6 +432,20 @@ COM_DECLSPEC_NOTHROW STDMETHODIMP CAccTextBase::get_offsetAtPoint(long x, long y
     css::awt::Point point;
     point.X = x;
     point.Y = y;
+
+    if (coordType == IA2_COORDTYPE_SCREEN_RELATIVE)
+    {
+        // convert from screen to local coordinates
+        Reference<XAccessibleContext> xContext = pUNOInterface->getAccessibleContext();
+        Reference<XAccessibleComponent> xComponent(xContext, UNO_QUERY);
+        if (!xComponent.is())
+            return S_FALSE;
+
+        css::awt::Point aObjectPos = xComponent->getLocationOnScreen();
+        point.X -= aObjectPos.X;
+        point.Y -= aObjectPos.Y;
+    }
+
     *offset = GetXInterface()->getIndexAtPoint(point);
     return S_OK;