Re: transparent canvas working in gtkextra-2?

gtk_plot_canvas_set_transparent simply does not draw a background color. 
This is useful when you want to superimpose the plots on a background in 
a presentation, when you export it as an image (jpeg/gif/whatever).

Al Hooton wrote:

>	Hi, Adrian:
>
>	Thanks for responding so quickly, I truly do appreciate it.  Let me
>describe more of what I'm trying to do.
>
>	I have a situation where I want to display just a plot when the
>application is in one operating mode, and optionally display a sheet
>"under" the plot when the application is in a second operating mode.  In
>the second mode, the user will enter data in the sheet, and I will
>update the plot "over" the sheet as new data is entered.
>
>	In the descriptions below, the phrase "sw/sheet" will mean  a GtkSheet
>packed in to a ScrolledWindow container.
>
>	I first tried to use the fact that GtkCanvas is a subclass of GtkFixed,
>adding the plot as normal and adding the sw/sheet as a child of the
>canvas with gtk_fixed_put().  However, this doesn't work, because there
>is no way for the sw/sheet to be transparent (there are other side
>effects as well, but the fact that the sw/sheet can not be transparent
>causes this approach to not be workable for me).
>
>	The next thing I tried, and one that I think would work well if the
>canvas could be transparent, is the following (hopefully the ascii art
>will come through):
>
>GtkFixed
>  |
>  |--ScrolledWindow
>  |    |
>  |    |--GtkSheet
>  |
>  |--PlotCanvas
>       |
>       |--Plot
>
>	
>	In this solution, I would make the canvas/plot opaque when I did not
>want the user to see the sw/sheet, and I would make the canvas/plot
>transparent when I did want them to see the sw/sheet.  My tests so far
>have indicated this would work well, if only the canvas would become
>transparent when instructed to do so.  But, it does not.
>
>	This is why I am wondering how to get a canvas to be transparent, and
>if gtk_plot_canvas_set_transparent() works correctly in gtkextra-2?
>
>	I am definitely open to suggestions for other approaches to get the
>desired effect.
>
>	Thanks again, Adrian -- and to anybody else with some ideas to try!
>
>Regards,
>Al
>
>
>
>On Mon, 2004-02-09 at 11:02, Adrian E. Feiguin wrote:
>  
>
>>I still don't understand what you are trying to do, If you want to show 
>>other widgets, use the gtkfixed capabilities as I do with the buttons in 
>>testgtksheet. That's the only way to show other widgets inside a canvas. 
>>If what you want is to do something called MDI of Window in Window, 
>>that's not possible with gtk. You can use a notebook to diplay the plot 
>>in one tab and the sheets in other tabs. You can show buttons or icons 
>>in a canvas and get a sheet to appear on a different window when you 
>>click. Those are some ideas. But again, I still don't get it. What are 
>>you exactly trying to do?
>>Saludos,
>><ADRIAN>
>>
>>Al Hooton wrote:
>>
>>    
>>
>>>	Follow-up on this:
>>>
>>>	I have now spent pretty much the entire weekend going trying to get a
>>>canvas to be transparent in gtkextra-2.  It does not matter if the
>>>canvas has no plots, one plot, many plots -- the canvas will never go
>>>transparent so I can see what is behind it.
>>>
>>>	I've stepped through gtkplotcanvas.c, and related code, trying to
>>>figure out what is happening, but that has lead to a dead end.  It
>>>appears to me the code should work, in that it is not attempting to draw
>>>the main rectangle of the canvas when it is marked transparent. 
>>>However, it is still being drawn.  If I comment out the calls to
>>>gtk_plot_pc_draw_rectangle in gtk_plot_canvas_paint the rectangle is not
>>>drawn, but the canvas still appears to have a pixbuf that covers
>>>whatever is underneath.  I would have expected this pixbuf to be
>>>unrealized if the canvas widget is transparent, but I'm probably missing
>>>something in how this is supposed to work.
>>>
>>>	Has anybody successfully gotten a transparent canvas?  I'd really like
>>>to use the gtkextra-2 package for what I'm doing, but if the canvas can
>>>not be transparent I may have to abandon this for something else -- not
>>>my preference, since I already have so much work done on top of
>>>gtkextra-2.
>>>
>>>	Thanks!
>>>
>>>-- Al
>>>
>>>
>>>On Sat, 2004-02-07 at 20:20, Al Hooton wrote:
>>> 
>>>
>>>      
>>>
>>>>	Version: gtkextra-2 from CVS as a couple of weeks ago.
>>>>
>>>>	I have successfully been using multiple plots on a canvas, with all the
>>>>plots transparent.  Today for the first time, I tried making the canvas
>>>>transparent also, so I could see through the plots and the canvas to
>>>>what is below.  However, the canvas is not transparent when I set it
>>>>with gtk_plot_canvas_set_transparent().
>>>>
>>>>	I have tried a small test program that just creates a canvas as a child
>>>>of a parent window that has a blue background.  When I set the canvas to
>>>>transparent, I still have the while background of the canvas, instead of
>>>>seeing the blue background of the parent, so I know the canvas has not
>>>>become transparent.
>>>>
>>>>	Is this a known problem?  Do we have a workaround?
>>>>
>>>>	Thanks!
>>>>
>>>>-Al
>>>>
>>>>   
>>>>
>>>>        
>>>>
>>>
>>>
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>>>.
>>>
>>> 
>>>
>>>      
>>>
>>
>><!DSPAM:4027d98972192513720775>
>>    
>>
>
>.
>
>  
>



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