Change plot routine to take a drawing_area as argument

Previously we passed in width and height and the routine itself decided to
keep 5% margin around each edge - oddly doing this with double precision,
even though this is all integer coordinates.

Instead we are now passing in a drawing_area. We are kind of abusing the
cairo_rectangle_int_t data type here - but it seemed silly to redefine a
new data type for this.
Width and height give the size of the TOTAL drawing area (as before).
x and y give the offset from the edges - so the EFFECTIVE drawing area is
width-2x and height-2y
This is in preparation for adding tooltips - those need to know the
coordinate offsets from the edges - so having this hard coded inside the
plot function didn't make sense anymore.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

display.h

@@ -22,7 +22,7 @@ struct graphics_context {
 	double topy, bottomy;
 };
 
-extern void plot(struct graphics_context *gc, int w, int h, struct dive *dive);
+extern void plot(struct graphics_context *gc, cairo_rectangle_int_t *drawing_area, struct dive *dive);
 extern void set_source_rgb(struct graphics_context *gc, double r, double g, double b);
 
 #endif

gtk-gui.c

@@ -674,18 +674,21 @@ static gboolean expose_event(GtkWidget *widget, GdkEventExpose *event, gpointer
 {
 	struct dive *dive = current_dive;
 	struct graphics_context gc = { .printer = 0 };
-	int w,h;
+	static cairo_rectangle_int_t drawing_area;
 
-	w = widget->allocation.width;
+	/* the drawing area gives TOTAL width * height - x,y is used as the topx/topy offset
-	h = widget->allocation.height;
+	 * so effective drawing area is width-2x * height-2y */
+	drawing_area.width = widget->allocation.width;
+	drawing_area.height = widget->allocation.height;
+	drawing_area.x = drawing_area.width / 20.0;
+	drawing_area.y = drawing_area.height / 20.0;
 
 	gc.cr = gdk_cairo_create(widget->window);
 	set_source_rgb(&gc, 0, 0, 0);
 	cairo_paint(gc.cr);
 
 	if (dive)
-		plot(&gc, w, h, dive);
+		plot(&gc, &drawing_area, dive);
-
 	cairo_destroy(gc.cr);
 
 	return FALSE;

print.c

@@ -127,12 +127,13 @@ static void show_dive_text(struct dive *dive, cairo_t *cr, double w, double h, P
 
 static void show_dive_profile(struct dive *dive, cairo_t *cr, double w, double h)
 {
+	cairo_rectangle_int_t drawing_area = { w/20.0, h/20.0, w, h};
 	struct graphics_context gc = {
 		.printer = 1,
 		.cr = cr
 	};
 	cairo_save(cr);
-	plot(&gc, w, h, dive);
+	plot(&gc, &drawing_area, dive);
 	cairo_restore(cr);
 }
 

profile.c

@@ -722,14 +722,11 @@ static struct plot_info *create_plot_info(struct dive *dive)
 	return analyze_plot_info(pi);
 }
 
-void plot(struct graphics_context *gc, int w, int h, struct dive *dive)
+void plot(struct graphics_context *gc, cairo_rectangle_int_t *drawing_area, struct dive *dive)
 {
-	double topx, topy;
 	struct plot_info *pi = create_plot_info(dive);
 
-	topx = w / 20.0;
+	cairo_translate(gc->cr, drawing_area->x, drawing_area->y);
-	topy = h / 20.0;
-	cairo_translate(gc->cr, topx, topy);
 	cairo_set_line_width(gc->cr, 2);
 	cairo_set_line_cap(gc->cr, CAIRO_LINE_CAP_ROUND);
 	cairo_set_line_join(gc->cr, CAIRO_LINE_JOIN_ROUND);
@@ -741,8 +738,8 @@ void plot(struct graphics_context *gc, int w, int h, struct dive *dive)
 	 *
 	 * Snif. What a pity.
 	 */
-	gc->maxx = (w - 2*topx);
+	gc->maxx = (drawing_area->width - 2*drawing_area->x);
-	gc->maxy = (h - 2*topy);
+	gc->maxy = (drawing_area->height - 2*drawing_area->y);
 
 	/* Temperature profile */
 	plot_temperature_profile(gc, pi);