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--- calling_20object_20methods_20using_20structures [2018/03/31 13:19] – external edit 127.0.0.1
+++ calling_20object_20methods_20using_20structures [2024/01/05 00:22] (current) – external edit 127.0.0.1
@@ Line 1: / Line 1: @@
 =====Calling object methods using structures=====
-//by Richard Russell, March 2007//\\ \\  Calling **COM**, **OLE** or **ActiveX** object //methods// generally involves the use of a rather arcane syntax, such as this example taken from the BB4W manual under [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|Displaying GIF and JPEG images]]:\\ \\
+//by Richard Russell, March 2007//\\ \\  Calling **COM**, **OLE** or **ActiveX** object //methods// generally involves the use of a rather arcane syntax, such as this example taken from the BB4W manual under [[http://www.bbcbasic.co.uk/bbcwin/manual/bbcwine.html#gifjpeg|Displaying GIF and JPEG images]]:
+<code bb4w>
         SYS !(!gpp%+24), gpp%, ^hmw% : REM. IPicture::get_Width
         SYS !(!gpp%+28), gpp%, ^hmh% : REM. IPicture::get_Height
-Here it is not at all clear what methods are being called, and how, hence the need for comments.\\ \\  It is possible to improve the clarity considerably by using a **structure** to represent the object. You can then call the object's methods as follows:\\ \\
+</code>
+Here it is not at all clear what methods are being called, and how, hence the need for comments.\\ \\  It is possible to improve the clarity considerably by using a **structure** to represent the object. You can then call the object's methods as follows:
+<code bb4w>
         SYS IPicture.get_Width%, gpp%, ^hmw%
         SYS IPicture.get_Height%, gpp%, ^hmh%
-To make this work you need to declare a structure containing all the object's methods in the correct order. In the case of the **IPicture** interface the structure needs to be declared as follows:\\ \\
+</code>
+To make this work you need to declare a structure containing all the object's methods in the correct order. In the case of the **IPicture** interface the structure needs to be declared as follows:
+<code bb4w>
         DIM IPicture{QueryInterface%, AddRef%, Release%, get_Handle%, get_hPal%, \
         \            get_Type%, get_Width%, get_Height%, Render%, set_hPal%, get_CurDC%, \
         \            SelectPicture%, get_KeepOriginalFormat%, put_KeepOriginalFormat%, \
         \            PictureChanged%, SaveAsFile%, get_Attributes%}
-To complete the process we must point the structure at the object's dispatch table:\\ \\
+</code>
-        !(^IPicture{}+4) = !gpp%
-The memory originally allocated when the structure was created is wasted, but this isn't a problem if it is declared as a **LOCAL** structure.\\ \\  As a practical illustration of the use of this technique here is a replacement for the **PROCdisplay** routine listed in the BB4W manual:\\ \\
+To complete the process we must point the structure at the object's dispatch table:
+<code bb4w>
+        PTR(IPicture{}) = !gpp%
+</code>
+The memory originally allocated when the structure was created is wasted, but this isn't a problem if it is declared as a **LOCAL** structure.\\ \\  As a practical illustration of the use of this technique here is a replacement for the **PROCdisplay** routine listed in the BB4W manual:
+<code bb4w>
         DEF PROCdisplay(picture$, xpos%, ypos%, xsize%, ysize%)
         LOCAL iid{}, IPicture{}, oleaut32%, olpp%, gpp%, hmw%, hmh%, picture%, res%
@@ Line 37: / Line 55: @@
         IF gpp% = 0 ERROR 100, "OleLoadPicturePath failed"
-        !(^IPicture{}+4) = !gpp%
+        PTR(IPicture{}) = !gpp%
         SYS IPicture.get_Width%, gpp%, ^hmw%
@@ Line 49: / Line 67: @@
         SYS "UpdateWindow", @hwnd%
         ENDPROC
+</code>