[Freeciv-Dev] NEW BUFFER CODE TO SDLClient

[Rafał Bursig <bursig@xxxxxxxxx>]

Hi

  Attached code is new buffer engine to SDLClient.

Till now SDLClient has only one buffer
- main client buffer.

 draw :
                                                flush
  sprite -> main client buffer    ->     framebuffer.

All draw was done to this buffer, then we had to call flush function ( 
manualy ) tu copy this buffer to framebuffer. This method was fast but 
have big overwrite problem ( when you redraw somthing you overwrite 
city text or gui widget ) and there still lack redraw sdl widget 
callback ( after redraw full screen map )
New code obsolete almost all of those problems but for price of speed. 
:(
Basic idea of new code is simple, there are 4 main screen buffers :
- main client buffer.
- map buffer ( for terrain, specials, unit, cities, etc )
- city desciption buffer ( for city text )
- gui/widgets buffer ( here is draw entire gui )

draw sequence : 1 , 2, 3, 4 , 5

 draw map buffer to main buffer
 draw city text buffer to main buffer
 draw gui buffer to main buffer
 draw main buffer to framebuffer.

I) unit or terrain

   gui buffer 4)-> city text buffer 3) -> map buffer 2) -> main buffer 
5) -> framebuffer
                                                              /\
                                                               | 
1)                                                                              
unit or terrain sprite
II) update city text

   gui buffer 4) -> city text buffer 3) -> map buffer 2) -> main 
buffer 5) -> framebuffer
                                   /\
                                    | 
1)                                 clear buffer and redraw city texts
III) widget action ( exp. press button )

   gui buffer 4) -> city text buffer 3) -> map buffer 2) -> main 
buffer 5) -> framebuffer
           /\
            | 1)                    widget acction

  Create map buffer didn't make any trouble. It has screen pixel 
coding and draw to screen is fast.
  City description buffer create on big problem becouse SDLClient use 
AA text. This AA is reslut of use alpha chanel on font color. When we 
want use buffored text then this buffor must have alpha chanel (RGBA 
surface 32bit pixel coding) to proper store AA text info. And this will 
cost during blit(draw) operation becouse there is alpha calculation. 
Additonal problem give SDL lib becouse all Alpha blit operation "lock" 
destination pixel alpha value and all result of Alpha draw has old dest 
alpha value.
exp.
    Buffer was filed partial transparent white ( r = 255, g = 255, b = 
244, a = 128 ).
    Next we blit (draw) on it notransparent black (r =0, g =0, b=0, a 
= 255 ) rect.
    Result is rect filed with color r = 0, g = 0, b = 0 , a = 128.
    When you blit this buffer to screen you see partial transparent 
white area with partial transparetn
    black area.

This is big problem becouse entire text buffer is filed with total 
transparent black ( r = 0, g = 0, b = 0, a = 0). All draw to such 
buffer must be done with disabled alpha calculation but this work fine 
if we use only freeciv text style ( no background ). When we want have 
civ3 text style we fill text arrea partial transparent background color 
and blit on it ( with alpha calculation ) text . I this way we get 
partial transparent text and that is wrong.
Solution on this problem is fix to SDL_ttf lib that make avilable 
createing AA text with partial transparent colored background. ( 
blended_shaded_2.diff). I send this patch to SDL_ttf lib maintainer but 
has no response. Any way If you want use this new buffered code you 
must patch SDL_ttf lib code and rebuild it.
  GUI buffer has the same problem that city desciption buffer ( must 
be RGBA ) but is solved by patching SDL_ttf lib. Other problem here is 
that entire gui code has hard coded destination draw to main client 
buffer, and must be rewriten to new buffer code ( this take lots of 
work ). Here is another problem with partial transparent 
dialogs/window. When those are draw above other dialogs/window, this 
draw must be done with disable alpha calculation and all other 
dlg/window areas are redrawed by upper dlg/windows, but this is current 
must be acceptable.
SPEED.
This is important aspect of this code becouse if you want redraw 
somthing on map you must atomaticaly redraw all buffers, and this take 
time.
                     alpha callc.
gui buffer   --------------------                           
slow            \
                                               \
                       alpha callc.       \
text buffer  --------------------------- > main buffer -> frame buffer
                          slow          
/                                           /
map buffer   ---------------
                         fast

All those buffer draw is make during flush time. To optimize ( speedup 
) this flush I create new flush code that is attached to this new 
buffer code. ( All draw are made only to buffers and draw area are 
saved in store rect. array. After last net packed come there is called 
flush function that flush all stored rects in one call)
Please send me timing output of this code.

Rafal


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4buffer.diff.bz2
Description: application/bzip

blended_shaded_2.diff
Description: Text document