static gboolean
i7_goo_canvas_item_get_onscreen_coordinates(GooCanvasItem *item, GooCanvas *canvas, gint *x, gint *y)
{
GooCanvasBounds bounds;
GtkAllocation allocation;
gdouble canvas_x, canvas_y;
gdouble top, bottom, left, right, item_x, item_y;
/* Find out the size and coordinates of the current viewport */
goo_canvas_get_bounds(canvas, &canvas_x, &canvas_y, NULL, NULL);
GtkWidget *scrolled_window = gtk_widget_get_parent(GTK_WIDGET(canvas));
g_assert(GTK_IS_SCROLLED_WINDOW(scrolled_window));
GtkAdjustment *adj = gtk_scrolled_window_get_hadjustment(GTK_SCROLLED_WINDOW(scrolled_window));
left = canvas_x + gtk_adjustment_get_value(adj);
right = left + gtk_adjustment_get_page_size(adj);
adj = gtk_scrolled_window_get_vadjustment(GTK_SCROLLED_WINDOW(scrolled_window));
top = canvas_y + gtk_adjustment_get_value(adj);
bottom = top + gtk_adjustment_get_page_size(adj);
/* Make sure item is currently displayed */
goo_canvas_item_get_bounds(item, &bounds);
if(bounds.x1 > right || bounds.x2 < left || bounds.y1 > bottom || bounds.y2 < top) {
g_warning("Node not onscreen in canvas");
return FALSE;
}
/* Find out the onscreen coordinates of the canvas viewport */
gtk_widget_get_allocation(GTK_WIDGET(canvas), &allocation);
if(x) {
item_x = bounds.x1;
*x = (gint)(item_x - left) + allocation.x;
}
if(y) {
item_y = bounds.y1;
*y = (gint)(item_y - top) + allocation.y;
}
return TRUE;
}
/**
* change the zoom by factor
*
* zoom origin when zooming in is the cursor
* zoom origin when zooming out is the center of the current viewport
*
* @param sheet
* @param factor values should be in the range of [0.5 .. 2]
*/
void
sheet_change_zoom (Sheet *sheet, gdouble factor)
{
g_return_if_fail (sheet);
g_return_if_fail (IS_SHEET (sheet));
Coords adju, r, pointer, delta, center, pagesize;
GtkAdjustment *hadj = NULL, *vadj = NULL;
GooCanvas *canvas;
gboolean b = FALSE;
canvas = GOO_CANVAS (sheet);
// if we scroll out, just use the center as focus
// mouse curser centered scroll out "feels" awkward
if (factor < 1.) {
goo_canvas_set_scale (canvas, factor * goo_canvas_get_scale (canvas));
return;
}
// get pointer position in pixels
// just skip the correction if we can not get the pointer
if (!sheet_get_pointer_pixel (sheet, &pointer.x, &pointer.y)) {
goo_canvas_set_scale (canvas, factor * goo_canvas_get_scale (canvas));
g_warning ("Failed to get cursor position.");
return;
}
// top left corner in pixels
b = sheet_get_adjustments (sheet, &hadj, &vadj);
if (b) {
adju.x = gtk_adjustment_get_value (hadj);
adju.y = gtk_adjustment_get_value (vadj);
// get the page size in pixels
pagesize.x = gtk_adjustment_get_page_size (hadj);
pagesize.y = gtk_adjustment_get_page_size (vadj);
} else {
//FIXME untested codepath, check for variable space conversion
//FIXME Pixel vs GooUnits
gdouble left, right, top, bottom;
goo_canvas_get_bounds (canvas, &left, &top, &right, &bottom);
pagesize.x = bottom - top;
pagesize.y = right - left;
adju.x = adju.y = 0.;
}
// calculate the center of the widget in pixels
center.x = adju.x + pagesize.x/2.;
center.y = adju.y + pagesize.y/2.;
// calculate the delta between the center and the pointer in pixels
// this is required as the center is the zoom target
delta.x = pointer.x - center.x;
delta.y = pointer.y - center.y;
// increase the top left position in pixels by our calculated delta
adju.x += delta.x;
adju.y += delta.y;
//convert to canvas coords
goo_canvas_convert_from_pixels (canvas, &adju.x, &adju.y);
//the center of the canvas is now our cursor position
goo_canvas_scroll_to (canvas, adju.x, adju.y);
//calculate a correction term
//for the case that we can not scroll the pane far enough to
//compensate the whole off-due-to-wrong-center-error
if (b) {
r.x = gtk_adjustment_get_value (hadj);
r.y = gtk_adjustment_get_value (vadj);
goo_canvas_convert_from_pixels (canvas, &r.x, &r.y);
//the correction term in goo coordinates, to be subtracted from the backscroll distance
r.x -= adju.x;
r.y -= adju.y;
} else {
r.x = r.y = 0.;
}
// no the center is our cursor position and we can safely call scale
goo_canvas_set_scale (canvas, factor * goo_canvas_get_scale (canvas));
// top left corner in pixels after scaling
if (b) {
adju.x = gtk_adjustment_get_value (hadj);
adju.y = gtk_adjustment_get_value (vadj);
} else {
adju.x = adju.y = 0.;
}
// gtk_adjustment_get_page_size is constant before and after scale
adju.x -= (delta.x) / sheet->priv->zoom;
adju.y -= (delta.y) / sheet->priv->zoom;
goo_canvas_convert_from_pixels (canvas, &adju.x, &adju.y);
goo_canvas_scroll_to (canvas, adju.x-r.x, adju.y-r.y);
gtk_widget_queue_draw (GTK_WIDGET (canvas));
}
