Android GUI system Surfaceflinger (Handlepageflip)

1.1.1 Handlepageflip

Pageflip can be understood as "paging". From this point of view, it should be related to the layer buffer-because it is a multiple buffering mechanism, at the appropriate time, we need to do "flip" action.

void Surfaceflinger::handlepageflip ()

{...

Const DISPLAYHARDWARE&HW = Graphicplane (0). Displayhardware ()//display with number 0

Const regionscreenregion (Hw.bounds ());//Entire screen area

Const layervector&currentlayers (MDRAWINGSTATE.LAYERSSORTEDBYZ);/* Current All layers*/

const BOOL Visibleregions = Lockpageflip (currentlayers); The following is a detailed analysis of this function, noting its return

Value is a bool type variable. */

if (Visibleregions | | Mvisibleregionsdirty) {//visible area changed

regionopaqueregion;//Opaque Area

Computevisibleregions (Currentlayers, Mdirtyregion, opaqueregion)/*step2. Calculate Visible Area * *

/*step3. Reconstruct the Mvisiblelayerssortedbyz, that is, the sort of all visible layers * *

Const size_t count= currentlayers.size ();

Mvisiblelayerssortedbyz.clear ()/Empty

Mvisiblelayerssortedbyz.setcapacity (count);//capacity

for (size_t i=0; i<count; i++) {

if (!currentlayers[i]->visibleregionscreen.isempty ())//Current layer has visible area

Mvisiblelayerssortedbyz.add (Currentlayers[i]);

}

Mwormholeregion = Screenregion.subtract (opaqueregion);/*step4. Worm Hole Calculation * *

Mvisibleregionsdirty = false;

Invalidatehwcgeometry ();

}

Unlockpageflip (currentlayers);/*step5 with Lockpageflip.

...

Mdirtyregion.andself (screenregion);//Excluding areas outside the screen range

}