[wxPython-users] The grid control -- problems and questions

[Bob Klahn]

At 10:10 PM 9/3/2007, Robin wrote:
>Bob Klahn wrote:
>>The attached grid code features a custom renderer.  In that 
>>renderer, apart from drawing the given cell, I print the row, col, 
>>and isSelected values to stdout, along with the number of the 
>>current call to the draw routine (1, 2, 3, ...).
>>Some questions:
>>     (1) How do I best avoid the excessive drawing that occurs
>>              (a) when switching to another application and switching back?
>>              (b) when resizing the test frame?
>
>Which platform are you on?

Windows XP SP2

>If on the Mac then I think there is code in wxGrid that always 
>redraws all of the visible cells instead of optimizing it down as is 
>done on the other platforms.

>Otherwise only those cells that intersect with whatever region the 
>OS reports needs to be redrawn are painted.

Then, since

>The Grid class doesn't make use of any double buffering at all, and 
>would probably need to be rearchitected to be able to do so, but in 
>practice the method it does use is normally efficient enough.
>
>>     (2) Note the rows that are redrawn as one clicks on different rows.
>>              (a) When one clicks on the row immediately below the 
>> current row,
>>                       (i) notice the color of the rightmost column
>>                               -- Why is that happening?
>>                               -- Why is it different when moving 
>> from row 0 to row 1, versus
>>                                  moving from row n to row n+1 where n <> 0 ?
>
>I don't notice any color problem so I'm not quite sure what you are 
>talking about, but I do notice that you never specify in your 
>renderer's Draw method what the text foreground color should be, so 
>whatever it was set to previously in the DC will be used.  Perhaps 
>that is what you are seeing.
>
>
>>                       (ii) notice which rows are redrawn, and in what order
>>                               -- Why so many?
>>              (b) When one clicks on any row not immediately below 
>> the current row,
>>                       (i) notice that the color problem seen above 
>> does not occur
>>                               -- Why not?
>>                       (ii) notice that fewer rows are redrawn
>>                               -- Why?
>
>IIRC, when a new cell selected then the cells around the old one are 
>marked as needing refreshed because the cursor rectangle can overlap 
>the other cells by 1 pixel, so those cells end up getting redrawn to 
>be able to restore the border where the cursor used to be.