Author:admin

Date:2008-09-17T13:53:28.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@3 abb3cda0-5349-4a8f-a601-0c33ac3a8c38

documentation/current/platform-specifics/microsoft-windows/wel/wel-common-concepts/common-message-hooks.wiki

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+[[Property:title|Common message hooks]]
+[[Property:weight|4]]
+Each WEL library component implements a set of routines for processing the most common messages that a component receives. For example, looking at [[ref:libraries/wel/reference/wel_frame_window_chart|WEL_FRAME_WINDOW]] , you will see that there are many features which begin `on_'. Each of these features enable the user to know when a specific event has occurred, and to perform the appropriate processing as a result of this event. Most of the time, you will only be interested in a small subset of these, necessary to your program. For example, below is the code for on_paint:
+<code>
+	on_paint (paint_dc: WEL_PAINT_DC; invalid_rect: WEL_RECT) is
+			--Draw a centered text
+		do
+		end 
+</code>
+
+
+An on_paint message corresponds to the Wm_paint message generated by Windows whenever it needs to re-paint a window, and if you look at the feature, you can see that the arguments are a [[ref:libraries/wel/reference/wel_paint_dc_chart|WEL_PAINT_DC]]  and a[[ref:libraries/wel/reference/wel_rect_chart| WEL_RECT]] . which are relevant to this message. By redefining this feature (and others as required), your code will be able to respond appropriately to windows events. 
+{{note| '''Note'''. See [[Tutorial Step 2|step2]]  in the [[Tutorial|tutorial]]  for a simple demonstration involving the re-definition of <eiffel>on_left_button_down</eiffel>. }}
+
+
+For different messages received by a control, the arguments will differ (sometimes there are none), but those arguments will always be relevant to the message. For example, on_menu_command from [[ref:libraries/wel/reference/wel_composite_window_chart|WEL_COMPOSITE_WINDOW]]  has an <eiffel>INTEGER</eiffel> as an argument, the value of which is a unique menu identifier. <br/>
+
+{{note| '''Note'''. Not all windows events have a corresponding `on_' message hook defined in WEL. If you wish to process a Windows message that does not correspond to one of the available features, you will need to redefine process_message. <br/>
+}}
+
+
+
+
+

documentation/current/platform-specifics/microsoft-windows/wel/wel-common-concepts/index.wiki

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+[[Property:title|WEL Common Concepts]]
+[[Property:weight|0]]
+Some useful WEL concepts are listed below:
+*  [[Inheriting WEL_APPLICATION|Inheriting WEL_APPLICATION]]  
+*  [[Redefining main_window|Redefining main_window]]  
+*  [[Redefining `init_application'|Redefining init_application]]  
+*  [[Common message hooks|Common message hooks]]  
+
+
+
+

documentation/current/platform-specifics/microsoft-windows/wel/wel-common-concepts/inheriting-wel-application.wiki

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+[[Property:title|Inheriting WEL_APPLICATION]]
+[[Property:weight|1]]
+For most WEL applications that you write, you will need to inherit [[ref:libraries/wel/reference/wel_application_chart|WEL_APPLICATION]] . 
+
+{{note| '''Note'''. See [[Tutorial Step 1|step1]]  in the [[Tutorial|tutorial]]  for a simple demonstration of how to do this }}
+
+
+
+

documentation/current/platform-specifics/microsoft-windows/wel/wel-common-concepts/redefining-init-application.wiki

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+[[Property:title|Redefining `init_application']]
+[[Property:weight|2]]
+[[ref:libraries/wel/reference/wel_application_chart|WEL_APPLICATION]]  contains a feature <eiffel>init_application</eiffel> which does nothing by default, but is called before the application is started. This can be redefined to execute tasks that must be performed before the application is running. A common redefinition is to allow the loading of common dll's, see [[List View|list_view]]  sample for a demonstration of this technique. 
+
+
+
+

documentation/current/platform-specifics/microsoft-windows/wel/wel-common-concepts/redefining-main-window.wiki

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+[[Property:title|Redefining main_window]]
+[[Property:weight|1]]
+When you inherit [[ref:/libraries/wel/reference/wel_application_chart|WEL_APPLICATION]] , you will need to implement the deferred feature main_window as a once function. This will be the main window of your application, and can be any descendent of [[ref:libraries/wel/reference/wel_composite_window_chart|WEL_COMPOSITE_WINDOW]] . 
+
+{{note| '''Note'''. See [[Tutorial Step 2|step2]]  in the [[Tutorial|tutorial]]  for a simple demonstration of how to do this. }}
+
+
+
+