Luiz Americo Pereira Camara wrote:
While debugging scrolling bugs in LCL i found that ClientToScreen acts
differently according to the widget set.
These are the behaviors:
1) The returned value is related to the actual position, i.e., it does
not consider the scroll offset. If you pass Point(0,0) the value will be
the same regardless of the scroll position. (Gtk1)
2) The returned value is related to the virtual position, i.e, it takes
into account the scroll offset. If you pass Point(0, 0) the value
changes inversely to scrollbar position. (Gtk2)
3) The returned value is related to the virtual position, i.e, it takes
into account the scroll offset. If you pass Point(0, 0) the value
changes the same amount of scrollbar position. (Win32)
4) Nothing. Qt has no visible scrollbars so...
Notes:
Delphi does the same as (1)/Gtk1
Not really, internally Delphi does it like 2. All controls are moved.
(3) is clearly buggy.
Between (1) and (2) is a design decision.
We started like delphi, move controls and report corrected values when
asked. However this aproach is very inefficient on all widgetsets except
win32. So the new approach is that controls stay at their position and
only the "virtual parent" gets an offset.
This means that the top/left of a control on a say scrollbox are allways
the same, an offset to the "virtual parent" top/left.
So now ClientToScreen.
The top/left of a scrolled control needs to get a scrolled offset, so
that is reflects the "real" position relative to the "real" parent of
the control.
Marc
Attached is a patch that makes win32 acts like (2)/gtk2. It changes the
offset signal when calculating the LCL bounds. With the change it
becomes consistent with the TCustomGroupBox signal convention (LCL
bounds at Right/Down of win32 +, at Left/Up -).
It also fixes the scrolling paint and setcursor of non TWincontrol.
Luiz
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