/*
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version. 
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2007 Blender Foundation.
 * All rights reserved.
 *
 * 
 * Contributor(s): Blender Foundation
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/windowmanager/intern/wm_draw.c
 *  \ingroup wm
 */


#include <stdlib.h>
#include <string.h>
#include <GL/glew.h>

#include "DNA_listBase.h"
#include "DNA_screen_types.h"
#include "DNA_windowmanager_types.h"
#include "DNA_userdef_types.h"
#include "DNA_view3d_types.h"

#include "MEM_guardedalloc.h"

#include "BLI_blenlib.h"
#include "BLI_utildefines.h"

#include "BKE_context.h"
#include "BKE_global.h"


#include "GHOST_C-api.h"

#include "ED_screen.h"

#include "GPU_draw.h"
#include "GPU_extensions.h"

#include "RE_engine.h"

#include "WM_api.h"
#include "WM_types.h"
#include "wm.h"
#include "wm_draw.h"
#include "wm_window.h"
#include "wm_event_system.h"

/* swap */
#define WIN_NONE_OK		0
#define WIN_BACK_OK     1
#define WIN_FRONT_OK    2
#define WIN_BOTH_OK		3

/* ******************* drawing, overlays *************** */


static void wm_paintcursor_draw(bContext *C, ARegion *ar)
{
	wmWindowManager *wm= CTX_wm_manager(C);
	
	if(wm->paintcursors.first) {
		wmWindow *win= CTX_wm_window(C);
		bScreen *screen= win->screen;
		wmPaintCursor *pc;

		if(screen->subwinactive == ar->swinid) {
			for(pc= wm->paintcursors.first; pc; pc= pc->next) {
				if(pc->poll == NULL || pc->poll(C)) {
					ARegion *ar_other= CTX_wm_region(C);
					if (ELEM(win->grabcursor, GHOST_kGrabWrap, GHOST_kGrabHide)) {
						int x = 0, y = 0;
						wm_get_cursor_position(win, &x, &y);
						pc->draw(C, x - ar_other->winrct.xmin, y - ar_other->winrct.ymin, pc->customdata);
					} else {
						pc->draw(C, win->eventstate->x - ar_other->winrct.xmin, win->eventstate->y - ar_other->winrct.ymin, pc->customdata);
					}
				}
			}
		}
	}
}

/* ********************* drawing, swap ****************** */

static void wm_area_mark_invalid_backbuf(ScrArea *sa)
{
	if(sa->spacetype == SPACE_VIEW3D)
		((View3D*)sa->spacedata.first)->flag |= V3D_INVALID_BACKBUF;
}

static int wm_area_test_invalid_backbuf(ScrArea *sa)
{
	if(sa->spacetype == SPACE_VIEW3D)
		return (((View3D*)sa->spacedata.first)->flag & V3D_INVALID_BACKBUF);
	else
		return 1;
}

static void wm_region_test_render_do_draw(ScrArea *sa, ARegion *ar)
{
	if(sa->spacetype == SPACE_VIEW3D) {
		RegionView3D *rv3d = ar->regiondata;
		RenderEngine *engine = (rv3d)? rv3d->render_engine: NULL;

		if(engine && (engine->flag & RE_ENGINE_DO_DRAW)) {
			ar->do_draw = 1;
			engine->flag &= ~RE_ENGINE_DO_DRAW;
		}
	}
}

/********************** draw all **************************/
/* - reference method, draw all each time                 */

static void wm_method_draw_full(bContext *C, wmWindow *win)
{
	bScreen *screen= win->screen;
	ScrArea *sa;
	ARegion *ar;

	/* draw area regions */
	for(sa= screen->areabase.first; sa; sa= sa->next) {
		CTX_wm_area_set(C, sa);

		for(ar=sa->regionbase.first; ar; ar= ar->next) {
			if(ar->swinid) {
				CTX_wm_region_set(C, ar);
				ED_region_do_draw(C, ar);
				wm_paintcursor_draw(C, ar);
				ED_area_overdraw_flush(sa, ar);
				CTX_wm_region_set(C, NULL);
			}
		}
		
		wm_area_mark_invalid_backbuf(sa);
		CTX_wm_area_set(C, NULL);
	}

	ED_screen_draw(win);
	ED_area_overdraw(C);

	/* draw overlapping regions */
	for(ar=screen->regionbase.first; ar; ar= ar->next) {
		if(ar->swinid) {
			CTX_wm_menu_set(C, ar);
			ED_region_do_draw(C, ar);
			CTX_wm_menu_set(C, NULL);
		}
	}

	if(screen->do_draw_gesture)
		wm_gesture_draw(win);
}

/****************** draw overlap all **********************/
/* - redraw marked areas, and anything that overlaps it   */
/* - it also handles swap exchange optionally, assuming   */
/*   that on swap no clearing happens and we get back the */
/*   same buffer as we swapped to the front               */

/* mark area-regions to redraw if overlapped with rect */
static void wm_flush_regions_down(bScreen *screen, rcti *dirty)
{
	ScrArea *sa;
	ARegion *ar;

	for(sa= screen->areabase.first; sa; sa= sa->next) {
		for(ar= sa->regionbase.first; ar; ar= ar->next) {
			if(BLI_isect_rcti(dirty, &ar->winrct, NULL)) {
				ar->do_draw= RGN_DRAW;
				memset(&ar->drawrct, 0, sizeof(ar->drawrct));
				ar->swap= WIN_NONE_OK;
			}
		}
	}
}

/* mark menu-regions to redraw if overlapped with rect */
static void wm_flush_regions_up(bScreen *screen, rcti *dirty)
{
	ARegion *ar;
	
	for(ar= screen->regionbase.first; ar; ar= ar->next) {
		if(BLI_isect_rcti(dirty, &ar->winrct, NULL)) {
			ar->do_draw= RGN_DRAW;
			memset(&ar->drawrct, 0, sizeof(ar->drawrct));
			ar->swap= WIN_NONE_OK;
		}
	}
}

static void wm_method_draw_overlap_all(bContext *C, wmWindow *win, int exchange)
{
	wmWindowManager *wm= CTX_wm_manager(C);
	bScreen *screen= win->screen;
	ScrArea *sa;
	ARegion *ar;
	static rcti rect= {0, 0, 0, 0};

	/* after backbuffer selection draw, we need to redraw */
	for(sa= screen->areabase.first; sa; sa= sa->next)
		for(ar= sa->regionbase.first; ar; ar= ar->next)
			if(ar->swinid && !wm_area_test_invalid_backbuf(sa))
				ED_region_tag_redraw(ar);

	/* flush overlapping regions */
	if(screen->regionbase.first) {
		/* flush redraws of area regions up to overlapping regions */
		for(sa= screen->areabase.first; sa; sa= sa->next)
			for(ar= sa->regionbase.first; ar; ar= ar->next)
				if(ar->swinid && ar->do_draw)
					wm_flush_regions_up(screen, &ar->winrct);
		
		/* flush between overlapping regions */
		for(ar= screen->regionbase.last; ar; ar= ar->prev)
			if(ar->swinid && ar->do_draw)
				wm_flush_regions_up(screen, &ar->winrct);
		
		/* flush redraws of overlapping regions down to area regions */
		for(ar= screen->regionbase.last; ar; ar= ar->prev)
			if(ar->swinid && ar->do_draw)
				wm_flush_regions_down(screen, &ar->winrct);
	}

	/* flush drag item */
	if(rect.xmin!=rect.xmax) {
		wm_flush_regions_down(screen, &rect);
		rect.xmin= rect.xmax = 0;
	}
	if(wm->drags.first) {
		/* doesnt draw, fills rect with boundbox */
		wm_drags_draw(C, win, &rect);
	}
	
	/* draw marked area regions */
	for(sa= screen->areabase.first; sa; sa= sa->next) {
		CTX_wm_area_set(C, sa);

		for(ar=sa->regionbase.first; ar; ar= ar->next) {
			if(ar->swinid) {
				if(ar->do_draw) {
					CTX_wm_region_set(C, ar);
					ED_region_do_draw(C, ar);
					wm_paintcursor_draw(C, ar);
					ED_area_overdraw_flush(sa, ar);
					CTX_wm_region_set(C, NULL);

					if(exchange)
						ar->swap= WIN_FRONT_OK;
				}
				else if(exchange) {
					if(ar->swap == WIN_FRONT_OK) {
						CTX_wm_region_set(C, ar);
						ED_region_do_draw(C, ar);
						wm_paintcursor_draw(C, ar);
						ED_area_overdraw_flush(sa, ar);
						CTX_wm_region_set(C, NULL);

						ar->swap= WIN_BOTH_OK;
					}
					else if(ar->swap == WIN_BACK_OK)
						ar->swap= WIN_FRONT_OK;
					else if(ar->swap == WIN_BOTH_OK)
						ar->swap= WIN_BOTH_OK;
				}
			}
		}
		
		wm_area_mark_invalid_backbuf(sa);
		CTX_wm_area_set(C, NULL);
	}

	/* after area regions so we can do area 'overlay' drawing */
	if(screen->do_draw) {
		ED_screen_draw(win);

		if(exchange)
			screen->swap= WIN_FRONT_OK;
	}
	else if(exchange) {
		if(screen->swap==WIN_FRONT_OK) {
			ED_screen_draw(win);
			screen->swap= WIN_BOTH_OK;
		}
		else if(screen->swap==WIN_BACK_OK)
			screen->swap= WIN_FRONT_OK;
		else if(screen->swap==WIN_BOTH_OK)
			screen->swap= WIN_BOTH_OK;
	}

	ED_area_overdraw(C);

	/* draw marked overlapping regions */
	for(ar=screen->regionbase.first; ar; ar= ar->next) {
		if(ar->swinid && ar->do_draw) {
			CTX_wm_menu_set(C, ar);
			ED_region_do_draw(C, ar);
			CTX_wm_menu_set(C, NULL);
		}
	}

	if(screen->do_draw_gesture)
		wm_gesture_draw(win);
	
	/* needs pixel coords in screen */
	if(wm->drags.first) {
		wm_drags_draw(C, win, NULL);
	}
}

#if 0
/******************** draw damage ************************/
/* - not implemented                                      */

static void wm_method_draw_damage(bContext *C, wmWindow *win)
{
	wm_method_draw_all(C, win);
}
#endif

/****************** draw triple buffer ********************/
/* - area regions are written into a texture, without any */
/*   of the overlapping menus, brushes, gestures. these   */
/*   are redrawn each time.                               */
/*                                                        */
/* - if non-power of two textures are supported, that is  */
/*   used. if not, multiple smaller ones are used, with   */
/*   worst case wasted space being 23.4% for 3x3 textures */

#define MAX_N_TEX 3

typedef struct wmDrawTriple {
	GLuint bind[MAX_N_TEX*MAX_N_TEX];
	int x[MAX_N_TEX], y[MAX_N_TEX];
	int nx, ny;
	GLenum target;
} wmDrawTriple;

static int is_pow2(int n)
{
	return ((n)&(n-1))==0;
}

static int smaller_pow2(int n)
{
	while (!is_pow2(n))
		n= n&(n-1);

	return n;
}

static int larger_pow2(int n)
{
	if (is_pow2(n))
		return n;

	while(!is_pow2(n))
		n= n&(n-1);

	return n*2;
}

static void split_width(int x, int n, int *splitx, int *nx)
{
	int a, newnx, waste;

	/* if already power of two just use it */
	if(is_pow2(x)) {
		splitx[0]= x;
		(*nx)++;
		return;
	}

	if(n == 1) {
		/* last part, we have to go larger */
		splitx[0]= larger_pow2(x);
		(*nx)++;
	}
	else {
		/* two or more parts to go, use smaller part */
		splitx[0]= smaller_pow2(x);
		newnx= ++(*nx);
		split_width(x-splitx[0], n-1, splitx+1, &newnx);

		for(waste=0, a=0; a<n; a++)
			waste += splitx[a];

		/* if we waste more space or use the same amount,
		 * revert deeper splits and just use larger */
		if(waste >= larger_pow2(x)) {
			splitx[0]= larger_pow2(x);
			memset(splitx+1, 0, sizeof(int)*(n-1));
		}
		else
			*nx= newnx;
	}
}

static void wm_draw_triple_free(wmWindow *win)
{
	if(win->drawdata) {
		wmDrawTriple *triple= win->drawdata;

		glDeleteTextures(triple->nx*triple->ny, triple->bind);

		MEM_freeN(triple);

		win->drawdata= NULL;
	}
}

static void wm_draw_triple_fail(bContext *C, wmWindow *win)
{
	wm_draw_window_clear(win);

	win->drawfail= 1;
	wm_method_draw_overlap_all(C, win, 0);
}

static int wm_triple_gen_textures(wmWindow *win, wmDrawTriple *triple)
{
	GLint maxsize;
	int x, y;

	/* compute texture sizes */
	if(GLEW_ARB_texture_rectangle || GLEW_NV_texture_rectangle || GLEW_EXT_texture_rectangle) {
		triple->target= GL_TEXTURE_RECTANGLE_ARB;
		triple->nx= 1;
		triple->ny= 1;
		triple->x[0]= win->sizex;
		triple->y[0]= win->sizey;
	}
	else if(GPU_non_power_of_two_support()) {
		triple->target= GL_TEXTURE_2D;
		triple->nx= 1;
		triple->ny= 1;
		triple->x[0]= win->sizex;
		triple->y[0]= win->sizey;
	}
	else {
		triple->target= GL_TEXTURE_2D;
		triple->nx= 0;
		triple->ny= 0;
		split_width(win->sizex, MAX_N_TEX, triple->x, &triple->nx);
		split_width(win->sizey, MAX_N_TEX, triple->y, &triple->ny);
	}

	/* generate texture names */
	glGenTextures(triple->nx*triple->ny, triple->bind);

	if(!triple->bind[0]) {
		/* not the typical failure case but we handle it anyway */
		printf("WM: failed to allocate texture for triple buffer drawing (glGenTextures).\n");
		return 0;
	}

	for(y=0; y<triple->ny; y++) {
		for(x=0; x<triple->nx; x++) {
			/* proxy texture is only guaranteed to test for the cases that
			 * there is only one texture in use, which may not be the case */
			glGetIntegerv(GL_MAX_TEXTURE_SIZE, &maxsize);

			if(triple->x[x] > maxsize || triple->y[y] > maxsize) {
				glBindTexture(triple->target, 0);
				printf("WM: failed to allocate texture for triple buffer drawing (texture too large for graphics card).\n");
				return 0;
			}

			/* setup actual texture */
			glBindTexture(triple->target, triple->bind[x + y*triple->nx]);
			glTexImage2D(triple->target, 0, GL_RGB8, triple->x[x], triple->y[y], 0, GL_RGB, GL_UNSIGNED_BYTE, NULL);
			glTexParameteri(triple->target, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
			glTexParameteri(triple->target, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
			// glColor still used with this enabled?
			// glTexEnvi(triple->target, GL_TEXTURE_ENV_MODE, GL_REPLACE);
			glBindTexture(triple->target, 0);

			/* not sure if this works everywhere .. */
			if(glGetError() == GL_OUT_OF_MEMORY) {
				printf("WM: failed to allocate texture for triple buffer drawing (out of memory).\n");
				return 0;
			}
		}
	}

	return 1;
}

static void wm_triple_draw_textures(wmWindow *win, wmDrawTriple *triple)
{
	float halfx, halfy, ratiox, ratioy;
	int x, y, sizex, sizey, offx, offy;

	glEnable(triple->target);

	for(y=0, offy=0; y<triple->ny; offy+=triple->y[y], y++) {
		for(x=0, offx=0; x<triple->nx; offx+=triple->x[x], x++) {
			sizex= (x == triple->nx-1)? win->sizex-offx: triple->x[x];
			sizey= (y == triple->ny-1)? win->sizey-offy: triple->y[y];

			/* wmOrtho for the screen has this same offset */
			ratiox= sizex;
			ratioy= sizey;
			halfx= 0.375f;
			halfy= 0.375f;

			/* texture rectangle has unnormalized coordinates */
			if(triple->target == GL_TEXTURE_2D) {
				ratiox /= triple->x[x];
				ratioy /= triple->y[y];
				halfx /= triple->x[x];
				halfy /= triple->y[y];
			}

			glBindTexture(triple->target, triple->bind[x + y*triple->nx]);

			glColor3f(1.0f, 1.0f, 1.0f);
			glBegin(GL_QUADS);
				glTexCoord2f(halfx, halfy);
				glVertex2f(offx, offy);

				glTexCoord2f(ratiox+halfx, halfy);
				glVertex2f(offx+sizex, offy);

				glTexCoord2f(ratiox+halfx, ratioy+halfy);
				glVertex2f(offx+sizex, offy+sizey);

				glTexCoord2f(halfx, ratioy+halfy);
				glVertex2f(offx, offy+sizey);
			glEnd();
		}
	}

	glBindTexture(triple->target, 0);
	glDisable(triple->target);
}

static void wm_triple_copy_textures(wmWindow *win, wmDrawTriple *triple)
{
	int x, y, sizex, sizey, offx, offy;

	for(y=0, offy=0; y<triple->ny; offy+=triple->y[y], y++) {
		for(x=0, offx=0; x<triple->nx; offx+=triple->x[x], x++) {
			sizex= (x == triple->nx-1)? win->sizex-offx: triple->x[x];
			sizey= (y == triple->ny-1)? win->sizey-offy: triple->y[y];

			glBindTexture(triple->target, triple->bind[x + y*triple->nx]);
			glCopyTexSubImage2D(triple->target, 0, 0, 0, offx, offy, sizex, sizey);
		}
	}

	glBindTexture(triple->target, 0);
}

static void wm_method_draw_triple(bContext *C, wmWindow *win)
{
	wmWindowManager *wm= CTX_wm_manager(C);
	wmDrawTriple *triple;
	bScreen *screen= win->screen;
	ScrArea *sa;
	ARegion *ar;
	int copytex= 0, paintcursor= 1;

	if(win->drawdata) {
		glClearColor(0, 0, 0, 0);
		glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

		wmSubWindowSet(win, screen->mainwin);

		wm_triple_draw_textures(win, win->drawdata);
	}
	else {
		win->drawdata= MEM_callocN(sizeof(wmDrawTriple), "wmDrawTriple");

		if(!wm_triple_gen_textures(win, win->drawdata))
		{
			wm_draw_triple_fail(C, win);
			return;
		}
	}

	triple= win->drawdata;

	/* draw marked area regions */
	for(sa= screen->areabase.first; sa; sa= sa->next) {
		CTX_wm_area_set(C, sa);

		for(ar=sa->regionbase.first; ar; ar= ar->next) {
			if(ar->swinid && ar->do_draw) {
				CTX_wm_region_set(C, ar);
				ED_region_do_draw(C, ar);
				ED_area_overdraw_flush(sa, ar);
				CTX_wm_region_set(C, NULL);
				copytex= 1;
			}
		}
		
		wm_area_mark_invalid_backbuf(sa);
		CTX_wm_area_set(C, NULL);
	}

	if(copytex) {
		wmSubWindowSet(win, screen->mainwin);
		ED_area_overdraw(C);

		wm_triple_copy_textures(win, triple);
	}

	/* after area regions so we can do area 'overlay' drawing */
	ED_screen_draw(win);

	/* draw overlapping regions */
	for(ar=screen->regionbase.first; ar; ar= ar->next) {
		if(ar->swinid) {
			CTX_wm_menu_set(C, ar);
			ED_region_do_draw(C, ar);
			CTX_wm_menu_set(C, NULL);
			/* when a menu is being drawn, don't do the paint cursors */
			paintcursor= 0;
		}
	}

	/* always draw, not only when screen tagged */
	if(win->gesture.first)
		wm_gesture_draw(win);

	if(paintcursor && wm->paintcursors.first) {
		for(sa= screen->areabase.first; sa; sa= sa->next) {
			for(ar=sa->regionbase.first; ar; ar= ar->next) {
				if(ar->swinid == screen->subwinactive) {
					CTX_wm_area_set(C, sa);
					CTX_wm_region_set(C, ar);

					/* make region ready for draw, scissor, pixelspace */
					ED_region_set(C, ar);
					wm_paintcursor_draw(C, ar);

					CTX_wm_region_set(C, NULL);
					CTX_wm_area_set(C, NULL);
				}
			}
		}

		wmSubWindowSet(win, screen->mainwin);
	}
	
	/* needs pixel coords in screen */
	if(wm->drags.first) {
		wm_drags_draw(C, win, NULL);
	}

}

/****************** main update call **********************/

/* quick test to prevent changing window drawable */
static int wm_draw_update_test_window(wmWindow *win)
{
	ScrArea *sa;
	ARegion *ar;
	int do_draw= 0;

	for(ar= win->screen->regionbase.first; ar; ar= ar->next) {
		if(ar->do_draw_overlay) {
			wm_tag_redraw_overlay(win, ar);
			ar->do_draw_overlay= 0;
		}
		if(ar->swinid && ar->do_draw)
			do_draw= 1;
	}

	for(sa= win->screen->areabase.first; sa; sa= sa->next) {
		for(ar=sa->regionbase.first; ar; ar= ar->next) {
			wm_region_test_render_do_draw(sa, ar);

			if(ar->swinid && ar->do_draw)
				do_draw = 1;
		}
	}

	if(do_draw)
		return 1;
	
	if(win->screen->do_refresh)
		return 1;
	if(win->screen->do_draw)
		return 1;
	if(win->screen->do_draw_gesture)
		return 1;
	if(win->screen->do_draw_paintcursor)
		return 1;
	if(win->screen->do_draw_drag)
		return 1;
	
	return 0;
}

static int wm_automatic_draw_method(wmWindow *win)
{
	/* Ideally all cards would work well with triple buffer, since if it works
	   well gives the least redraws and is considerably faster at partial redraw
	   for sculpting or drawing overlapping menus. For typically lower end cards
	   copy to texture is slow though and so we use overlap instead there. */

	if(win->drawmethod == USER_DRAW_AUTOMATIC) {
		/* ATI opensource driver is known to be very slow at this */
		if(GPU_type_matches(GPU_DEVICE_ATI, GPU_OS_UNIX, GPU_DRIVER_OPENSOURCE))
			return USER_DRAW_OVERLAP;
		/* also Intel drivers are slow */
		else if(GPU_type_matches(GPU_DEVICE_INTEL, GPU_OS_UNIX, GPU_DRIVER_ANY))
			return USER_DRAW_OVERLAP;
		else if(GPU_type_matches(GPU_DEVICE_INTEL, GPU_OS_WIN, GPU_DRIVER_ANY))
			return USER_DRAW_OVERLAP_FLIP;
		else if(GPU_type_matches(GPU_DEVICE_INTEL, GPU_OS_MAC, GPU_DRIVER_ANY))
			return USER_DRAW_OVERLAP_FLIP;
		/* Windows software driver darkens color on each redraw */
		else if(GPU_type_matches(GPU_DEVICE_SOFTWARE, GPU_OS_WIN, GPU_DRIVER_SOFTWARE))
			return USER_DRAW_OVERLAP_FLIP;
		else if(GPU_type_matches(GPU_DEVICE_SOFTWARE, GPU_OS_UNIX, GPU_DRIVER_SOFTWARE))
			return USER_DRAW_OVERLAP;
		/* drawing lower color depth again degrades colors each time */
		else if(GPU_color_depth() < 24)
			return USER_DRAW_OVERLAP;
		else
			return USER_DRAW_TRIPLE;
	}
	else
		return win->drawmethod;
}

void wm_tag_redraw_overlay(wmWindow *win, ARegion *ar)
{
	/* for draw triple gestures, paint cursors don't need region redraw */
	if(ar && win) {
		if(wm_automatic_draw_method(win) != USER_DRAW_TRIPLE)
			ED_region_tag_redraw(ar);
		win->screen->do_draw_paintcursor= 1;
	}
}

void wm_draw_update(bContext *C)
{
	wmWindowManager *wm= CTX_wm_manager(C);
	wmWindow *win;
	int drawmethod;

	GPU_free_unused_buffers();
	
	for(win= wm->windows.first; win; win= win->next) {
		if(win->drawmethod != U.wmdrawmethod) {
			wm_draw_window_clear(win);
			win->drawmethod= U.wmdrawmethod;
		}

		if(wm_draw_update_test_window(win)) {
			CTX_wm_window_set(C, win);
			
			/* sets context window+screen */
			wm_window_make_drawable(C, win);

			/* notifiers for screen redraw */
			if(win->screen->do_refresh)
				ED_screen_refresh(wm, win);

			drawmethod= wm_automatic_draw_method(win);

			if(win->drawfail)
				wm_method_draw_overlap_all(C, win, 0);
			else if(drawmethod == USER_DRAW_FULL)
				wm_method_draw_full(C, win);
			else if(drawmethod == USER_DRAW_OVERLAP)
				wm_method_draw_overlap_all(C, win, 0);
			else if(drawmethod == USER_DRAW_OVERLAP_FLIP)
				wm_method_draw_overlap_all(C, win, 1);
			else // if(drawmethod == USER_DRAW_TRIPLE)
				wm_method_draw_triple(C, win);

			win->screen->do_draw_gesture= 0;
			win->screen->do_draw_paintcursor= 0;
			win->screen->do_draw_drag= 0;
		
			wm_window_swap_buffers(win);

			CTX_wm_window_set(C, NULL);
		}
	}
}

void wm_draw_window_clear(wmWindow *win)
{
	bScreen *screen= win->screen;
	ScrArea *sa;
	ARegion *ar;
	int drawmethod= wm_automatic_draw_method(win);

	if(drawmethod == USER_DRAW_TRIPLE)
		wm_draw_triple_free(win);

	/* clear screen swap flags */
	if(screen) {
		for(sa= screen->areabase.first; sa; sa= sa->next)
			for(ar=sa->regionbase.first; ar; ar= ar->next)
				ar->swap= WIN_NONE_OK;
		
		screen->swap= WIN_NONE_OK;
	}
}

void wm_draw_region_clear(wmWindow *win, ARegion *ar)
{
	int drawmethod= wm_automatic_draw_method(win);

	if(ELEM(drawmethod, USER_DRAW_OVERLAP, USER_DRAW_OVERLAP_FLIP))
		wm_flush_regions_down(win->screen, &ar->winrct);

	win->screen->do_draw= 1;
}