[gthumb] grid view: spread the thumbnails horizontally to fill the space

[Paolo Bacchilega <paobac src gnome org>]

commit 793feee8e9dcf3dd3421056d9786c9bea27f077b
Author: Paolo Bacchilega <paobac src gnome org>
Date:   Mon Jan 7 12:36:39 2019 +0100

    grid view: spread the thumbnails horizontally to fill the space

 gthumb/gth-grid-view.c | 66 ++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 58 insertions(+), 8 deletions(-)
---
diff --git a/gthumb/gth-grid-view.c b/gthumb/gth-grid-view.c
index c5414f38..8b7ee6ac 100644
--- a/gthumb/gth-grid-view.c
+++ b/gthumb/gth-grid-view.c
@@ -160,7 +160,8 @@ struct _GthGridViewPrivate {
        int                    thumbnail_size;
        int                    thumbnail_border;
        int                    cell_size;           /* max size of any cell area */
-       int                    cell_spacing;        /* space between adjacent cell areas both horizontally 
and vertically */
+       int                    cell_spacing;        /* vertical space and mininum horizontal space between 
adjacent cell areas */
+       double                 cell_x_spacing;      /* horizontal space between adjacent cell areas 
(calculated automatically to fill the horizontal space uniformly). */
        int                    cell_padding;        /* space between the cell area border and its content */
        int                    caption_spacing;     /* space between the thumbnail area and the caption area 
*/
        int                    caption_padding;     /* space between the caption area border and its content 
*/
@@ -736,7 +737,7 @@ static void
 _gth_grid_view_layout_line (GthGridView     *self,
                            GthGridViewLine *line)
 {
-       int    x;
+       double x;
        int    direction;
        GList *scan;
 
@@ -752,9 +753,10 @@ _gth_grid_view_layout_line (GthGridView     *self,
        for (scan = line->items; scan; scan = scan->next) {
                GthGridViewItem *item = scan->data;
 
-               x += direction * self->priv->cell_spacing;
-               _gth_grid_view_place_item_at (self, item, x, line->y);
+               x += direction * self->priv->cell_x_spacing;
+               _gth_grid_view_place_item_at (self, item, round (x), line->y);
                x += direction * self->priv->cell_size;
+               x += direction * self->priv->cell_x_spacing;
        }
 }
 
@@ -1141,18 +1143,63 @@ gth_grid_view_get_preferred_height (GtkWidget *widget,
 }
 
 
+static void
+_gth_grid_view_relayout_lines (GthGridView *self)
+{
+       GList *scan;
+
+       for (scan = self->priv->lines; scan; scan = scan->next) {
+               GthGridViewLine *line = scan->data;
+               _gth_grid_view_layout_line (self, line);
+       }
+
+       gtk_widget_queue_draw (GTK_WIDGET (self));
+}
+
+
+static double
+round_to_0_2 (double n)
+{
+       double i = floor (n);
+       double f = n - i;
+       double r = 0;
+
+       if (f < 0.1)
+               r = 0;
+       else if (f < 0.3)
+               r = 0.2;
+       else if (f < 0.5)
+               r = 0.4;
+       else if (f < 0.7)
+               r = 0.6;
+       else if (f < 0.9)
+               r = 0.8;
+       else
+               r = 1.0;
+       return i + r;
+}
+
+
 static void
 gth_grid_view_size_allocate (GtkWidget     *widget,
                             GtkAllocation *allocation)
 {
        GthGridView *self;
        int          old_cells_per_line;
+       int          new_cells_per_line;
+       double       new_cell_x_spacing;
+       gboolean     cell_x_spacing_changed;
 
        self = GTH_GRID_VIEW (widget);
 
        old_cells_per_line = gth_grid_view_get_items_per_line (self);
        self->priv->width = allocation->width;
 
+       new_cells_per_line = gth_grid_view_get_items_per_line (self);
+       new_cell_x_spacing = round_to_0_2 ((((double) self->priv->width / new_cells_per_line) - 
self->priv->cell_size) / 2.0);
+       cell_x_spacing_changed = (new_cell_x_spacing != self->priv->cell_x_spacing);
+       self->priv->cell_x_spacing = new_cell_x_spacing;
+
        gtk_widget_set_allocation (widget, allocation);
 
        if (gtk_widget_get_realized (widget)) {
@@ -1165,10 +1212,12 @@ gth_grid_view_size_allocate (GtkWidget     *widget,
                                   MAX (self->priv->width, allocation->width),
                                   MAX (self->priv->height, allocation->height));
 
-               if (self->priv->needs_relayout || (old_cells_per_line != gth_grid_view_get_items_per_line 
(self))) {
+               if (self->priv->needs_relayout || (old_cells_per_line != new_cells_per_line)) {
                        self->priv->make_focused_visible = TRUE;
                        _gth_grid_view_queue_relayout (self);
                }
+               else if (cell_x_spacing_changed)
+                       _gth_grid_view_relayout_lines (self);
        }
        else
                self->priv->needs_relayout_after_size_allocate = TRUE;
@@ -1723,9 +1772,9 @@ _gth_grid_view_draw_drop_target (GthGridView *self,
 
        x = 0;
        if (self->priv->drop_pos == GTH_DROP_POSITION_LEFT)
-               x = item->area.x - (self->priv->cell_spacing / 2);
+               x = item->area.x - (self->priv->cell_x_spacing / 2);
        else if (self->priv->drop_pos == GTH_DROP_POSITION_RIGHT)
-               x = item->area.x + self->priv->cell_size + (self->priv->cell_spacing / 2);
+               x = item->area.x + self->priv->cell_size + (self->priv->cell_x_spacing / 2);
 
        gtk_render_focus (style_context,
                           cr,
@@ -2596,7 +2645,7 @@ _gth_grid_view_get_drop_target_at (GthGridView *self,
        row = MAX (row, 0);
 
        items_per_line = gth_grid_view_get_items_per_line (self);
-       col = (x - (self->priv->cell_spacing / 2)) / (self->priv->cell_size + self->priv->cell_spacing) + 1;
+       col = (x - (self->priv->cell_x_spacing / 2)) / (self->priv->cell_size + self->priv->cell_x_spacing) + 
1;
        col = MIN (col, items_per_line);
 
        return (items_per_line * row) + col - 1;
@@ -3954,6 +4003,7 @@ gth_grid_view_init (GthGridView *self)
 
        /* self->priv->cell_size = 0; */
        self->priv->cell_spacing = DEFAULT_CELL_SPACING;
+       self->priv->cell_x_spacing = -1;
        /* self->priv->cell_padding = DEFAULT_CELL_PADDING; */
        self->priv->caption_spacing = DEFAULT_CAPTION_SPACING;
        self->priv->caption_padding = DEFAULT_CAPTION_PADDING;