[cairo] Cairo Drawing Speed

[Duong Hoang Linh]

Hi Maarten,

I think i used win32 surface. Below is the code for initializing my 
cairo structure before drawing:

    //Cairo structures
    cairo_surface_t *surface;
    cairo_t *cr;

    int ww, wh;
    RECT rc;
    GetWindowRect(&rc);
    ww = (rc.right - rc.left);
    wh = (rc.bottom - rc.top);

    HDC memdc;
    HBITMAP hbuffer;

    memdc = CreateCompatibleDC(paintDC.m_hDC);
    hbuffer = CreateCompatibleBitmap(paintDC.m_hDC, ww, wh);
    SelectObject(memdc, hbuffer);

    surface = cairo_win32_surface_create (memdc);  // to the memory DC
    cr = cairo_create (surface);

It may be a good idea to use image surface. I will try out and compare.

Thanks!

Maarten Bosmans wrote:
> Your code looks like the right way to construct these lines.
>
> What backend are you using? It could very well be that using an
> imagesurface to draw the lines and then blit the result to the screen
> is faster.
>
> And of course it is always faster if the lines are aligned on the
> pixel grid, but in your case that's probably not possible because of
> diagonal line segments.
>
> Maarten
>
>
> 2009/11/24 Duong Hoang Linh <linh.duong at quantuminventions.com>:
>   
>> Hi Emmanuel,
>>
>> This is my code for drawing line:
>>
>>     cairo_set_source_rgb (cr, 0, 0, 0);
>>     cairo_set_line_width (cr, 7);
>>     cairo_set_line_cap  (cr, CAIRO_LINE_CAP_ROUND);
>>     cairo_set_line_join (cr, CAIRO_LINE_JOIN_ROUND);
>>
>>     for(int k=0;k<vLines.size();k++)
>>     {
>>         cairo_move_to (cr, vLines[k].ptLineArray[0].x, vLines[k].ptLineArray[0].y);
>>         for(int i=1;i<vLines[k].numLinePoints;i++)
>>             cairo_line_to (cr, vLines[k].ptLineArray[i].x, vLines[k].ptLineArray[i].y);
>>     }
>>
>>     cairo_stroke_preserve (cr);
>>
>>     cairo_set_source_rgb (cr, 1, 1, 1);
>>     cairo_set_line_width (cr, 4);
>>
>>     cairo_stroke (cr);
>>
>> I run this code on wince 5.0 device, processor ARM920T, 40MB RAM.
>>
>> In more detail, i measure the time execution of cairo_stroke and it takes
>> from 100-120ms. And in total, i need to do cairo_stroke 6 times, which add
>> up to 700+ms.
>>
>> Thanks.
>>