[evince/wip/link-preview: 1/2] libview: Make a preview popover for links

[Germán Poo-Caamaño <gpoo src gnome org>]

commit d68471a3f70d207a95684e5c5be4a1836b9a3c2b
Author: Mads Chr. Olesen <mads mchro dk>
Date:   Wed Nov 2 18:52:33 2016 +0100

    libview: Make a preview popover for links
    
    Inspired by Wikipedia showing a preview of the contents of footnotes,
    show a preview of the target of internal links in the tooltip (as a
    popover).
    
    Fixes #662

 libview/ev-jobs.c         |   2 +-
 libview/ev-view-private.h |  17 +++++
 libview/ev-view.c         | 186 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 199 insertions(+), 6 deletions(-)
---
diff --git a/libview/ev-jobs.c b/libview/ev-jobs.c
index f24808b0..c96e92cb 100644
--- a/libview/ev-jobs.c
+++ b/libview/ev-jobs.c
@@ -894,7 +894,7 @@ ev_job_thumbnail_run (EvJob *job)
         }
 
        if ((job_thumb->format == EV_JOB_THUMBNAIL_PIXBUF && pixbuf == NULL) ||
-            job_thumb->thumbnail_surface == NULL) {
+           (job_thumb->format != EV_JOB_THUMBNAIL_PIXBUF && job_thumb->thumbnail_surface == NULL)) {
                ev_job_failed (job,
                               EV_DOCUMENT_ERROR,
                               EV_DOCUMENT_ERROR_INVALID,
diff --git a/libview/ev-view-private.h b/libview/ev-view-private.h
index 02562ddd..6cad627f 100644
--- a/libview/ev-view-private.h
+++ b/libview/ev-view-private.h
@@ -131,6 +131,15 @@ typedef struct {
        EvAnnotation *annot;
 } MovingAnnotInfo;
 
+/* Information for handling link preview thumbnails */
+typedef struct {
+       EvJob           *job;
+       gdouble         left;
+       gdouble         top;
+       GtkWidget       *popover;
+       EvLink          *link;
+} EvLinkPreview;
+
 struct _EvView {
        GtkContainer layout;
 
@@ -261,6 +270,9 @@ struct _EvView {
        /* Current zoom center */
        gdouble zoom_center_x;
        gdouble zoom_center_y;
+
+       /* Link preview */
+       EvLinkPreview link_preview;
 };
 
 struct _EvViewClass {
@@ -311,6 +323,10 @@ void _ev_view_transform_doc_point_to_view_point (EvView   *view,
                                                 int       page,
                                                 EvPoint  *doc_point,
                                                 GdkPoint *view_point);
+void _ev_view_transform_doc_point_by_rotation_scale (EvView   *view,
+                                                int       page,
+                                                EvPoint  *doc_point,
+                                                GdkPoint *view_point);
 void _ev_view_transform_doc_rect_to_view_rect (EvView       *view,
                                               int           page,
                                               EvRectangle  *doc_rect,
@@ -322,6 +338,7 @@ gint _ev_view_get_caret_cursor_offset_at_doc_point (EvView *view,
                                                    gint    page,
                                                    gdouble doc_x,
                                                    gdouble doc_y);
+void _ev_view_cleanup_link_preview_popover (EvView     *view);
 
 void _ev_view_clear_selection (EvView   *view);
 void _ev_view_set_selection   (EvView   *view,
diff --git a/libview/ev-view.c b/libview/ev-view.c
index 805744ef..d03a1e7c 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -1428,7 +1428,7 @@ _ev_view_transform_view_rect_to_doc_rect (EvView       *view,
 }
 
 void
-_ev_view_transform_doc_point_to_view_point (EvView   *view,
+_ev_view_transform_doc_point_by_rotation_scale (EvView   *view,
                                            int       page,
                                            EvPoint  *doc_point,
                                            GdkPoint *view_point)
@@ -1475,8 +1475,25 @@ _ev_view_transform_doc_point_to_view_point (EvView   *view,
 
        view_x = CLAMP ((gint)(x * view->scale + 0.5), 0, page_area.width);
        view_y = CLAMP ((gint)(y * view->scale + 0.5), 0, page_area.height);
-       view_point->x = view_x + page_area.x + border.left;
-       view_point->y = view_y + page_area.y + border.top;
+
+       view_point->x = view_x;
+       view_point->y = view_y;
+}
+
+void
+_ev_view_transform_doc_point_to_view_point (EvView   *view,
+                                           int       page,
+                                           EvPoint  *doc_point,
+                                           GdkPoint *view_point)
+{
+       GdkRectangle page_area;
+       GtkBorder border;
+       _ev_view_transform_doc_point_by_rotation_scale (view, page, doc_point, view_point);
+
+       ev_view_get_page_extents (view, page, &page_area, &border);
+
+       view_point->x = view_point->x + page_area.x + border.left;
+       view_point->y = view_point->y + page_area.y + border.top;
 }
 
 void
@@ -4296,6 +4313,8 @@ ev_view_scroll_event (GtkWidget *widget, GdkEventScroll *event)
        guint state;
        gboolean fit_width, fit_height;
 
+       _ev_view_cleanup_link_preview_popover (view);
+
        state = event->state & gtk_accelerator_get_default_mod_mask ();
 
        if (state == GDK_CONTROL_MASK) {
@@ -4913,6 +4932,69 @@ get_annot_area (EvView       *view,
                                       annot, area);
 }
 
+static void
+link_preview_show_thumbnail (GdkPixbuf *pixbuf, EvView *view)
+{
+       GtkWidget *popover = view->link_preview.popover;
+       gdouble         left = view->link_preview.left;
+       gdouble         top = view->link_preview.top;
+       int             width = MIN(gdk_pixbuf_get_width (pixbuf) - left, gtk_widget_get_allocated_width 
(GTK_WIDGET (view)));
+       int             height = MIN (gdk_pixbuf_get_height (pixbuf) - top, 365);
+       GdkPixbuf       *thumbnail_slice;
+       GtkWidget *image_view;
+
+       thumbnail_slice = gdk_pixbuf_new_subpixbuf (pixbuf,
+                                                   (int)left, (int)top,
+                                                   width, height);
+       image_view = gtk_image_new_from_pixbuf (thumbnail_slice);
+
+       gtk_widget_destroy (gtk_bin_get_child (GTK_BIN (popover)));
+       gtk_container_add (GTK_CONTAINER (popover), image_view);
+       gtk_widget_show (image_view);
+
+       g_object_unref (thumbnail_slice);
+}
+
+static void
+link_preview_job_finished_cb (EvJobThumbnail *job,
+                               EvView *view)
+{
+       GtkWidget *popover = view->link_preview.popover;
+       GdkPixbuf *pixbuf;
+       if (ev_job_is_failed (EV_JOB (job))) {
+               gtk_widget_destroy (popover);
+               view->link_preview.popover = NULL;
+               g_object_unref (job);
+               view->link_preview.job = NULL;
+               return;
+       }
+
+       if (ev_document_model_get_inverted_colors (view->model)) {
+               ev_document_misc_invert_surface (job->thumbnail_surface);
+       }
+
+       pixbuf = ev_document_misc_pixbuf_from_surface (job->thumbnail_surface);
+
+       link_preview_show_thumbnail (pixbuf, view);
+
+       g_object_unref (pixbuf);
+       g_object_unref (job);
+       view->link_preview.job = NULL;
+}
+
+void
+_ev_view_cleanup_link_preview_popover (EvView  *view) {
+       if (view->link_preview.job) {
+               ev_job_cancel (view->link_preview.job);
+               g_object_unref (view->link_preview.job);
+               view->link_preview.job = NULL;
+       }
+       if (view->link_preview.popover) {
+               gtk_widget_destroy (view->link_preview.popover);
+               view->link_preview.popover = NULL;
+       }
+}
+
 static gboolean
 ev_view_query_tooltip (GtkWidget  *widget,
                       gint        x,
@@ -4942,18 +5024,102 @@ ev_view_query_tooltip (GtkWidget  *widget,
        }
 
        link = ev_view_get_link_at_location (view, x, y);
-       if (!link)
+
+       if (!link) {
+               _ev_view_cleanup_link_preview_popover (view);
+               view->link_preview.link = NULL;
                return FALSE;
+       }
 
        text = tip_from_link (view, link);
        if (text && g_utf8_validate (text, -1, NULL)) {
-               GdkRectangle link_area;
+               GdkRectangle     link_area;
+               EvLinkAction    *action;
+               EvLinkDest      *dest;
+               EvLinkDestType   type;
+               EvPoint          link_dest_doc;
+               GdkPoint         link_dest_view;
+               guint            link_dest_page;
+               GtkWidget       *popover, *spinner;
+               cairo_surface_t *page_surface = NULL;
 
                get_link_area (view, x, y, link, &link_area);
                gtk_tooltip_set_text (tooltip, text);
                gtk_tooltip_set_tip_area (tooltip, &link_area);
                g_free (text);
 
+               if (link == view->link_preview.link)
+                       return TRUE;
+
+               /* Display thumbnail, if applicable */
+               action = ev_link_get_action (link);
+               if (!action) return TRUE;
+               dest = ev_link_action_get_dest (action);
+               if (!dest) return TRUE;
+               type = ev_link_dest_get_dest_type (dest);
+
+               if (type == EV_LINK_DEST_TYPE_NAMED) {
+                       dest = ev_document_links_find_link_dest (EV_DOCUMENT_LINKS (view->document),
+                                                                ev_link_dest_get_named_dest (dest));
+               }
+
+               _ev_view_cleanup_link_preview_popover (view);
+
+               /* Init popover */
+               view->link_preview.popover = popover = gtk_popover_new (GTK_WIDGET (view));
+               gtk_popover_set_pointing_to (GTK_POPOVER (popover), &link_area);
+               gtk_popover_set_modal (GTK_POPOVER (popover), FALSE);
+
+               spinner = gtk_spinner_new ();
+               gtk_spinner_start (GTK_SPINNER (spinner));
+               gtk_container_add (GTK_CONTAINER (popover) , spinner);
+               gtk_widget_show (spinner);
+
+               /* Start thumbnailing job async */
+               link_dest_page = ev_link_dest_get_page (dest);
+               view->link_preview.job = ev_job_thumbnail_new (view->document,
+                                                              link_dest_page,
+                                                              view->rotation,
+                                                              view->scale);
+               ev_job_thumbnail_set_output_format (EV_JOB_THUMBNAIL (view->link_preview.job),
+                                                   EV_JOB_THUMBNAIL_SURFACE);
+
+               link_dest_doc.x = ev_link_dest_get_left (dest, NULL);
+               link_dest_doc.y = ev_link_dest_get_top (dest, NULL);
+               _ev_view_transform_doc_point_by_rotation_scale (view,
+                                                               link_dest_page,
+                                                               &link_dest_doc,
+                                                               &link_dest_view);
+               view->link_preview.left = link_dest_view.x;
+               view->link_preview.top = link_dest_view.y;
+               view->link_preview.link = link;
+
+               page_surface = ev_pixbuf_cache_get_surface (view->pixbuf_cache,
+                                                           link_dest_page);
+
+               if (page_surface) {
+                       GdkPixbuf *slice;
+
+                       slice = gdk_pixbuf_get_from_surface (page_surface, 0, 0,
+                                      cairo_image_surface_get_width (page_surface),
+                                      cairo_image_surface_get_height (page_surface));
+                       link_preview_show_thumbnail (slice, view);
+
+                       g_object_unref (slice);
+               }
+               else {
+                       g_signal_connect (view->link_preview.job, "finished",
+                                         G_CALLBACK (link_preview_job_finished_cb),
+                                         view);
+                       ev_job_scheduler_push_job (view->link_preview.job,
+                                                  EV_JOB_PRIORITY_LOW);
+               }
+
+               if (type == EV_LINK_DEST_TYPE_NAMED)
+                       g_object_unref (dest);
+
+               gtk_widget_show (popover);
+
                return TRUE;
        }
        g_free (text);
@@ -5152,6 +5318,8 @@ ev_view_button_press_event (GtkWidget      *widget,
 {
        EvView *view = EV_VIEW (widget);
 
+       _ev_view_cleanup_link_preview_popover (view);
+
        if (!view->document || ev_document_get_n_pages (view->document) <= 0)
                return FALSE;
 
@@ -6667,6 +6835,8 @@ ev_view_key_press_event (GtkWidget   *widget,
        EvView  *view = EV_VIEW (widget);
        gboolean retval;
 
+       _ev_view_cleanup_link_preview_popover(view);
+
        if (!view->document)
                return FALSE;
 
@@ -7256,6 +7426,12 @@ ev_view_dispose (GObject *object)
                view->child_focus_idle_id = 0;
        }
 
+       if (view->link_preview.job) {
+               ev_job_cancel (view->link_preview.job);
+               g_object_unref (view->link_preview.job);
+               view->link_preview.job = NULL;
+       }
+
         gtk_scrollable_set_hadjustment (GTK_SCROLLABLE (view), NULL);
         gtk_scrollable_set_vadjustment (GTK_SCROLLABLE (view), NULL);