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Diffstat (limited to 'docs/gui_and_events.txt')
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diff --git a/docs/gui_and_events.txt b/docs/gui_and_events.txt deleted file mode 100644 index 2e348e8d..00000000 --- a/docs/gui_and_events.txt +++ /dev/null @@ -1,75 +0,0 @@ - -Date: Thu, 17 May 2007 09:27:18 +0200 -From: Graeme Geldenhuys <graemeg@spamfilter.co.za> -Newsgroups: fpgui.development -Subject: Re: How does the gui part works? - - -Felipe Monteiro de Carvalho wrote: -> -> I only looked deep at the Gfx backend, so could you try to sumarize how -> does the GUI part works? -> -> I am trying to debug a crash on the lcl interface, where it crashes on -> TEVENTOBJ__SENDTOCHILD -> -> I see that fpGUI has message handling routines, message handling -> classes, and several other things, but I find this a little confusing. -> fpGfx already has message handling classes, and message handling -> procedures, so it seams like we have the same thing implemented twice. - -OK the GFX part gets events from the windowing system, be that X11 or -GDI. That means that TFCustomWindow gets all the events from the -windowing system. - -Now the GUI part. Every widget is *not* a TFCustomWindow, so every -widget doesn't have a Handle. The GUI is implemented with only one -handle per Form (TFForm). All widgets are just painted onto the canvas -of the TFForm. - -If you look at the TFCustomForm you will see it has a instance of -TFCustomWindow stored in FWnd. That instance gets all the events from -the windowing system. So to let the widgets also get events we have to -implement our own event system. The TFCustomForm will then send those -custom events (TEventObj descendants) by translating the windowing -events into our custom gui events. - -For example: - Lets say we have a Form with a Button on it. Now we want to handle a -OnMouseMove event on the Button. The flow of events will go as follows: - -1) TFCustomForm.Wnd will receive the OnMouseMove from the windowing -system and process it in the WndMouseMoved() method. - -2) WndMouseMoved() will translate that windowing system event into -whatever GUI events are needed and start sending them. - -3) Any TWidget descendant handles events in the ProcessEvent() method. -TWidget being the big one. - -4) Because TFCustomForm is a TFContainerWidget descendant, it means it -can contain other widgets. So it starts distributing the GUI events to -the children. Distribution is done by the DistributeEvent() method. - -5) If TFCustomButton needed to do any special processing with the GUI -event, it would handle it in its ProcessEvent() method. -TWidget.ProcessEvent normally does most of the generic work. - - 5.1) As an example of a widget that does custom processing, have a -look at the TFMenuItem.ProcessEvent(). In this case it handles the -TMouseEnterEventObj and TMouseLeaveEventObj events so it can changes -it's look when the mouse enters a menu item or leaves a menu item. - -So as a summary: - TFCustomForm contains a instance of a GFX window. Translates all the -GFX events (underlying windowing events) to GUI events (TEventObj -descendants) and distributes them to the children of the Form. - - -Hope that helps a bit.... - - --- -Graeme Geldenhuys -There is no place like S34° 03.168' E018° 49.342' - |