Make the knockout plotter calling behaviour optional by added a new entry

'option_knockout' to 'struct plotter_table' which basically is a request
from that plotter backend for the content redraw routine to get called in
such a way that overlapping render areas are avoided as much as possible.

It is up to the content redraw code to actually implement this
option if it is reasonably profitable.  This was and is currently done
explicitly by the html content redraw code.  On top of that the riscos
plotter code was installing the knockout plotter itself for all content
types except plaintext and SVG and this is no longer being done in this
patch.

In more detail:

- desktop/plotters.h: added struct plotter_table::option_knockout
- render/html_redraw.c(html_redraw): if the plotter backend wants the
knockout calling behaviour, install the knockout plotter which will then
call the real backend.  Also check on the return values of clg and clip
plotter calls.
- Plotter backend changes:
  -> no longer plotting in knockout mode:
     - gtk/gtk_print.c: Also removed a 2nd instance of
       "struct plotter_table plot".
     - riscos/save_draw.c
     - riscos/print.c: Also the path plotter function pointer wasn't
       filled in and this is now fixed.
     - pdf/pdf_plotters.c: Removed the flush function as this is
       optional and we only had a dummy implementation there.
  -> remaining to request knockout mode if it makes sense based on the
     content type:
     - gtk/gtk_plotters.c
     - riscos/plotters.c
     - desktop/knockout.c
- riscos/window.c: Removed what's believed an obsolete test on the
  content type which determined to additionally install the
  knockout plotter in front of the real plotter code.

svn path=/trunk/netsurf/; revision=4823

10 files changed, 41 insertions, 56 deletions

diff --git a/desktop/knockout.c b/desktop/knockout.c
index 4a82dc47f..658503313 100644
--- a/desktop/knockout.c
+++ b/desktop/knockout.c
@@ -38,7 +38,6 @@ struct knockout_entry;
 
 
 static void knockout_set_plotters(void);
-static bool knockout_plot_flush(void);
 static void knockout_calculate(int x0, int y0, int x1, int y1, struct knockout_box *box);
 static bool knockout_plot_fill_recursive(struct knockout_box *box, colour c);
 static bool knockout_plot_bitmap_tile_recursive(struct knockout_box *box,
@@ -50,8 +49,6 @@ static bool knockout_plot_rectangle(int x0, int y0, int width, int height,
 static bool knockout_plot_line(int x0, int y0, int x1, int y1, int width,
 		colour c, bool dotted, bool dashed);
 static bool knockout_plot_polygon(int *p, unsigned int n, colour fill);
-static bool knockout_plot_path(float *p, unsigned int n, colour fill,
-		float width, colour c, float *transform);
 static bool knockout_plot_fill(int x0, int y0, int x1, int y1, colour c);
 static bool knockout_plot_clip(int clip_x0, int clip_y0,
 		int clip_x1, int clip_y1);
@@ -65,8 +62,11 @@ static bool knockout_plot_bitmap(int x, int y, int width, int height,
 static bool knockout_plot_bitmap_tile(int x, int y, int width, int height,
 		struct bitmap *bitmap, colour bg,
 		bool repeat_x, bool repeat_y, struct content *content);
+static bool knockout_plot_flush(void);
 static bool knockout_plot_group_start(const char *name);
 static bool knockout_plot_group_end(void);
+static bool knockout_plot_path(float *p, unsigned int n, colour fill,
+		float width, colour c, float *transform);
 
 
 const struct plotter_table knockout_plotters = {
@@ -85,6 +85,7 @@ const struct plotter_table knockout_plotters = {
 	knockout_plot_group_end,
 	knockout_plot_flush,
 	knockout_plot_path,
+	true
 };
 
 
diff --git a/desktop/plotters.h b/desktop/plotters.h
index 16e0d47e6..2e7502c37 100644
--- a/desktop/plotters.h
+++ b/desktop/plotters.h
@@ -52,11 +52,12 @@ struct plotter_table {
 	bool (*bitmap_tile)(int x, int y, int width, int height,
 			struct bitmap *bitmap, colour bg,
 			bool repeat_x, bool repeat_y, struct content *content);
-	bool (*group_start)(const char *name);	/** optional */
-	bool (*group_end)(void);	/** optional */
-	bool (*flush)(void);
+	bool (*group_start)(const char *name); /**< optional, may be NULL */
+	bool (*group_end)(void); /**< optional, may be NULL */
+	bool (*flush)(void); /**< optional, may be NULL */
 	bool (*path)(float *p, unsigned int n, colour fill, float width,
 			colour c, float *transform);
+	bool option_knockout; /**< when set, avoid areas are replotted more than once.  */
 };
 
 /** Current plotters, must be assigned before use. */
diff --git a/gtk/gtk_plotters.c b/gtk/gtk_plotters.c
index 7a696e84a..9532119fd 100644
--- a/gtk/gtk_plotters.c
+++ b/gtk/gtk_plotters.c
@@ -93,7 +93,8 @@ const struct plotter_table nsgtk_plotters = {
 	NULL,
 	NULL,
 	NULL,
-	nsgtk_plot_path
+	nsgtk_plot_path,
+	true
 };
 
 
diff --git a/gtk/gtk_print.c b/gtk/gtk_print.c
index f32fcc64e..6f1bf976c 100644
--- a/gtk/gtk_print.c
+++ b/gtk/gtk_print.c
@@ -92,8 +92,6 @@ static void gtk_print_end(void);
 
 static GdkRectangle cliprect;
 
-struct plotter_table plot;
-
 static const struct plotter_table nsgtk_print_plotters = {
 	nsgtk_print_plot_clg,
 	nsgtk_print_plot_rectangle,
@@ -109,7 +107,8 @@ static const struct plotter_table nsgtk_print_plotters = {
 	NULL,
 	NULL,
 	NULL,
-	nsgtk_print_plot_path
+	nsgtk_print_plot_path,
+	false
 };
 
 static const struct printer gtk_printer= {
diff --git a/pdf/pdf_plotters.c b/pdf/pdf_plotters.c
index ac4e9b69c..6451ca704 100644
--- a/pdf/pdf_plotters.c
+++ b/pdf/pdf_plotters.c
@@ -64,7 +64,6 @@ static bool pdf_plot_bitmap(int x, int y, int width, int height,
 static bool pdf_plot_bitmap_tile(int x, int y, int width, int height,
 		struct bitmap *bitmap, colour bg,
 		bool repeat_x, bool repeat_y, struct content *content);
-static bool pdf_plot_flush(void);
 static bool pdf_plot_path(float *p, unsigned int n, colour fill, float width,
 		colour c, float *transform);
 
@@ -113,8 +112,9 @@ static const struct plotter_table pdf_plotters = {
 	pdf_plot_bitmap_tile,
 	NULL,
 	NULL,
-	pdf_plot_flush,
-	pdf_plot_path
+	NULL,
+	pdf_plot_path,
+	false
 };
 
 struct printer pdf_printer= {
@@ -515,19 +515,12 @@ HPDF_Image pdf_extract_image(struct bitmap *bitmap, struct content *content)
 	return image;
 }
 
-
-bool pdf_plot_flush(void)
-{
-	return true;
-}
-
-
-static inline float transform_x(float *transform,float x,float y)
+static inline float transform_x(float *transform, float x, float y)
 {
 	return ((transform[0] * x) + (transform[2] * (-y) ) + transform[4]) * 2;
 }
 
-static inline float transform_y(float *transform,float x,float y)
+static inline float transform_y(float *transform, float x, float y)
 {
 	return page_height - (((transform[1] * x) +
 			(transform[3] * (-y)) - transform[5]) * 2);
diff --git a/render/html_redraw.c b/render/html_redraw.c
index 6a6a0d170..16eb47dd3 100644
--- a/render/html_redraw.c
+++ b/render/html_redraw.c
@@ -115,24 +115,27 @@ bool html_redraw(struct content *c, int x, int y,
 		float scale, unsigned long background_colour)
 {
 	struct box *box;
-	bool result;
+	bool result, want_knockout;
 
 	box = c->data.html.layout;
 	assert(box);
 
-  	knockout_plot_start(&plot);
+	want_knockout = plot.option_knockout;
+	if (want_knockout)
+		knockout_plot_start(&plot);
 
 	/* clear to background colour */
-	plot.clip(clip_x0, clip_y0, clip_x1, clip_y1);
+	result = plot.clip(clip_x0, clip_y0, clip_x1, clip_y1);
 	if (c->data.html.background_colour != TRANSPARENT)
 		background_colour = c->data.html.background_colour;
-	plot.clg(background_colour);
+	result &= plot.clg(background_colour);
 
-	result = html_redraw_box(box, x, y,
+	result &= html_redraw_box(box, x, y,
 			clip_x0, clip_y0, clip_x1, clip_y1,
 			scale, background_colour, 0);
 
-	knockout_plot_end();
+	if (want_knockout)
+		knockout_plot_end();
 
 	return result;
 
diff --git a/riscos/plotters.c b/riscos/plotters.c
index 18b53701a..bfba10c39 100644
--- a/riscos/plotters.c
+++ b/riscos/plotters.c
@@ -77,6 +77,7 @@ const struct plotter_table ro_plotters = {
 	NULL,
 	NULL,
 	ro_plot_path,
+	true
 };
 
 int ro_plot_origin_x = 0;
diff --git a/riscos/print.c b/riscos/print.c
index 10296ebf3..e1474aa96 100644
--- a/riscos/print.c
+++ b/riscos/print.c
@@ -119,8 +119,8 @@ static bool print_fonts_plot_bitmap(int x, int y, int width, int height,
 static bool print_fonts_plot_bitmap_tile(int x, int y, int width, int height,
 		struct bitmap *bitmap, colour bg,
 		bool repeat_x, bool repeat_y, struct content *content);
-static bool print_fonts_plot_group_start(const char *name);
-static bool print_fonts_plot_group_end(void);
+static bool print_fonts_plot_path(float *p, unsigned int n, colour fill, float width,
+		colour c, float *transform);
 static void print_fonts_callback(void *context,
 		const char *font_name, unsigned int font_size,
 		const char *s8, unsigned short *s16, unsigned int n,
@@ -141,10 +141,11 @@ static const struct plotter_table print_fonts_plotters = {
 	print_fonts_plot_arc,
 	print_fonts_plot_bitmap,
 	print_fonts_plot_bitmap_tile,
-	print_fonts_plot_group_start,
-	print_fonts_plot_group_end,
 	NULL,
-	NULL
+	NULL,
+	NULL,
+	print_fonts_plot_path,
+	false
 };
 
 
@@ -629,6 +630,7 @@ bool print_document(struct gui_window *g, const char *filename)
 	}
 
 	plot = ro_plotters;
+	plot.option_knockout = false;
 	ro_plot_set_scale(print_scale);
 	ro_gui_current_redraw_gui = g;
 	current_redraw_browser = NULL;  /* we don't want to print the
@@ -863,11 +865,8 @@ bool print_fonts_plot_bitmap_tile(int x, int y, int width, int height,
 {
 	return true;
 }
-bool print_fonts_plot_group_start(const char *name)
-{
-	return true;
-}
-bool print_fonts_plot_group_end(void)
+bool print_fonts_plot_path(float *p, unsigned int n, colour fill, float width,
+		colour c, float *transform)
 {
 	return true;
 }
diff --git a/riscos/save_draw.c b/riscos/save_draw.c
index fd4208a52..dd9d32990 100644
--- a/riscos/save_draw.c
+++ b/riscos/save_draw.c
@@ -79,6 +79,7 @@ const struct plotter_table ro_save_draw_plotters = {
 	ro_save_draw_group_end,
 	NULL,
 	ro_save_draw_path,
+	false
 };
 
 static struct pencil_diagram *ro_save_draw_diagram;
diff --git a/riscos/window.c b/riscos/window.c
index 5da8662b6..571ed9af0 100644
--- a/riscos/window.c
+++ b/riscos/window.c
@@ -45,7 +45,6 @@
 #include "css/css.h"
 #include "desktop/browser.h"
 #include "desktop/frames.h"
-#include "desktop/knockout.h"
 #include "desktop/plotters.h"
 #include "desktop/textinput.h"
 #include "desktop/tree.h"
@@ -1409,11 +1408,9 @@ void ro_gui_window_redraw_all(void)
 void ro_gui_window_redraw(wimp_draw *redraw)
 {
 	osbool more;
-	bool knockout = true;
 	struct gui_window *g = (struct gui_window *)ro_gui_wimp_event_get_user_data(redraw->w);
 	float scale = g->bw->scale;
 	struct content *c = g->bw->current_content;
-	int clip_x0, clip_y0, clip_x1, clip_y1, clear_x1, clear_y1;
 	os_error *error;
 
 	/*	Handle no content quickly
@@ -1435,15 +1432,6 @@ void ro_gui_window_redraw(wimp_draw *redraw)
 	ro_gui_current_redraw_gui = g;
 	current_redraw_browser = g->bw;
 
-	/* rendering textplain has no advantages using knockout rendering other
-	 * than to slow things down. */
-	if (c->type == CONTENT_TEXTPLAIN 
-#ifdef WITH_NS_SVG
-		|| c->type == CONTENT_SVG
-#endif
-	)
-		knockout = false;
-
 	/* HTML rendering handles scale itself */
 	if (c->type == CONTENT_HTML)
 		scale = 1;
@@ -1456,6 +1444,8 @@ void ro_gui_window_redraw(wimp_draw *redraw)
 		return;
 	}
 	while (more) {
+		int clip_x0, clip_y0, clip_x1, clip_y1, clear_x1, clear_y1;
+
 		ro_plot_origin_x = redraw->box.x0 - redraw->xscroll;
 		ro_plot_origin_y = redraw->box.y1 - redraw->yscroll;
 		clip_x0 = (redraw->clip.x0 - ro_plot_origin_x) / 2;
@@ -1468,10 +1458,7 @@ void ro_gui_window_redraw(wimp_draw *redraw)
 		if (ro_gui_current_redraw_gui->option.buffer_everything)
 			ro_gui_buffer_open(redraw);
 
-		if (knockout) {
-			knockout_plot_start(&plot);
-			plot.clip(clip_x0, clip_y0, clip_x1, clip_y1);
-		}
+		plot.clip(clip_x0, clip_y0, clip_x1, clip_y1);
 
 		if (c->type != CONTENT_HTML)
 			plot.clg(0x00ffffff);
@@ -1481,8 +1468,7 @@ void ro_gui_window_redraw(wimp_draw *redraw)
 				clip_x0, clip_y0, clip_x1, clip_y1,
 				g->bw->scale,
 				0xFFFFFF);
-		if (knockout)
-			knockout_plot_end();
+
 		if (ro_gui_current_redraw_gui->option.buffer_everything)
 			ro_gui_buffer_close();