[evince/BUG_markup_annots_check_quadrilaterals: 8/8] markup annotations: use markup text region

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

commit 4cc58097a224b867d53a5f034c1e731645c8f2a0
Author: Nelson Benítez León <nbenitezl gmail com>
Date:   Sat Dec 28 20:31:54 2019 -0400

    markup annotations: use markup text region
    
    when determining if the mouse pointer is over
    a markup annotation (used by evince to change
    the pointer type). This is more accurate than
    just using the annot area.
    
    Implemented as a new libdocument method interface
    that we pass it the 'annotation' and 'x,y' coords
    and returns us whether that location is over the
    actual markup text of the annotation. The poppler
    implementation works by checking if there's any
    quadrilateral under that location.
    
    For pdf, quadrilaterals represent a more precise
    shape of the annotation than just the annotation
    area (which is currently used) so by checking
    the quads region we avoid false positives when
    hovering over blank space.
    
    The "point over a quadrilateral" code is based on:
    Algorithm: https://math.stackexchange.com/a/190203
    Implementation: https://stackoverflow.com/a/37865332
    
    Fixes issue #1275

 backend/pdf/ev-poppler.cc             | 83 +++++++++++++++++++++++++++++++++++
 libdocument/ev-document-annotations.c | 14 ++++++
 libdocument/ev-document-annotations.h | 15 +++++++
 libview/ev-view.c                     | 61 +++++++++++++++++++++++--
 4 files changed, 169 insertions(+), 4 deletions(-)
---
diff --git a/backend/pdf/ev-poppler.cc b/backend/pdf/ev-poppler.cc
index f5ab3e5e..911894b9 100644
--- a/backend/pdf/ev-poppler.cc
+++ b/backend/pdf/ev-poppler.cc
@@ -3926,6 +3926,88 @@ pdf_document_annotations_save_annotation (EvDocumentAnnotations *document_annota
        ev_document_set_modified (EV_DOCUMENT (document_annotations), TRUE);
 }
 
+/* Creates a vector from points @p1 and @p2 and stores it on @vector */
+static inline void
+set_vector (PopplerPoint *p1,
+           PopplerPoint *p2,
+           PopplerPoint *vector)
+{
+       vector->x = p2->x - p1->x;
+       vector->y = p2->y - p1->y;
+}
+
+/* Returns the dot product of the passed vectors @v1 and @v2 */
+static inline gdouble
+dot_product (PopplerPoint *v1,
+            PopplerPoint *v2)
+{
+       return v1->x * v2->x + v1->y * v2->y;
+}
+
+/* Algorithm: https://math.stackexchange.com/a/190203
+   Implementation: https://stackoverflow.com/a/37865332 */
+static gboolean
+point_over_poppler_quadrilateral (PopplerQuadrilateral *quad,
+                                 PopplerPoint         *M)
+{
+       PopplerPoint AB, AM, BC, BM;
+       gdouble dotABAM, dotABAB, dotBCBM, dotBCBC;
+
+       /* We interchange p3 and p4 because algorithm expects clockwise eg. p1 -> p2
+          while pdf quadpoints are defined as p1 -> p2                     p4 <- p3
+                                              p3 -> p4 (https://stackoverflow.com/q/9855814) */
+       set_vector (&quad->p1, &quad->p2, &AB);
+       set_vector (&quad->p1, M, &AM);
+       set_vector (&quad->p2, &quad->p4, &BC);
+       set_vector (&quad->p2, M, &BM);
+
+       dotABAM = dot_product (&AB, &AM);
+       dotABAB = dot_product (&AB, &AB);
+       dotBCBM = dot_product (&BC, &BM);
+       dotBCBC = dot_product (&BC, &BC);
+
+       return 0 <= dotABAM && dotABAM <= dotABAB && 0 <= dotBCBM && dotBCBM <= dotBCBC;
+}
+
+static EvAnnotationsOverMarkup
+pdf_document_annotations_over_markup (EvDocumentAnnotations *document_annotations,
+                                     EvAnnotation          *annot,
+                                     gdouble                x,
+                                     gdouble                y)
+{
+       EvPage       *page;
+       PopplerAnnot *poppler_annot;
+       GArray       *quads;
+       PopplerPoint  M;
+       guint         quads_len;
+       gdouble       height;
+
+       poppler_annot = POPPLER_ANNOT (g_object_get_data (G_OBJECT (annot), "poppler-annot"));
+
+       if (!poppler_annot || !POPPLER_IS_ANNOT_TEXT_MARKUP (poppler_annot))
+               return EV_ANNOTATION_OVER_MARKUP_UNKNOWN;
+
+       quads = poppler_annot_text_markup_get_quadrilaterals (POPPLER_ANNOT_TEXT_MARKUP (poppler_annot));
+       quads_len = quads->len;
+
+       page = ev_annotation_get_page (annot);
+       poppler_page_get_size (POPPLER_PAGE (page->backend_page), NULL, &height);
+       M.x = x;
+       M.y = height - y;
+
+       for (guint i = 0; i < quads_len; ++i) {
+               PopplerQuadrilateral *quadrilateral = &g_array_index (quads, PopplerQuadrilateral, i);
+
+               if (point_over_poppler_quadrilateral (quadrilateral, &M)) {
+                       g_array_unref (quads);
+                       return EV_ANNOTATION_OVER_MARKUP_YES;
+               }
+       }
+       g_array_unref (quads);
+
+       return EV_ANNOTATION_OVER_MARKUP_NOT;
+}
+
 static void
 pdf_document_document_annotations_iface_init (EvDocumentAnnotationsInterface *iface)
 {
@@ -3934,6 +4016,7 @@ pdf_document_document_annotations_iface_init (EvDocumentAnnotationsInterface *if
        iface->add_annotation = pdf_document_annotations_add_annotation;
        iface->save_annotation = pdf_document_annotations_save_annotation;
        iface->remove_annotation = pdf_document_annotations_remove_annotation;
+       iface->over_markup = pdf_document_annotations_over_markup;
 }
 
 /* Media */
diff --git a/libdocument/ev-document-annotations.c b/libdocument/ev-document-annotations.c
index 96ce4f6c..75fb4490 100644
--- a/libdocument/ev-document-annotations.c
+++ b/libdocument/ev-document-annotations.c
@@ -91,3 +91,17 @@ ev_document_annotations_can_remove_annotation (EvDocumentAnnotations *document_a
 
        return iface->remove_annotation != NULL;
 }
+
+EvAnnotationsOverMarkup
+ev_document_annotations_over_markup (EvDocumentAnnotations *document_annots,
+                                    EvAnnotation          *annot,
+                                    gdouble                x,
+                                    gdouble                y)
+{
+       EvDocumentAnnotationsInterface *iface = EV_DOCUMENT_ANNOTATIONS_GET_IFACE (document_annots);
+
+       if (iface->over_markup)
+               return iface->over_markup (document_annots, annot, x, y);
+
+       return EV_ANNOTATION_OVER_MARKUP_NOT_IMPLEMENTED;
+}
diff --git a/libdocument/ev-document-annotations.h b/libdocument/ev-document-annotations.h
index 36ec65ab..f0137c2b 100644
--- a/libdocument/ev-document-annotations.h
+++ b/libdocument/ev-document-annotations.h
@@ -66,6 +66,13 @@ typedef enum {
        EV_ANNOTATIONS_SAVE_ALL              = (1 << 11) - 1
 } EvAnnotationsSaveMask;
 
+typedef enum {
+       EV_ANNOTATION_OVER_MARKUP_NOT_IMPLEMENTED = 0,
+       EV_ANNOTATION_OVER_MARKUP_UNKNOWN,
+       EV_ANNOTATION_OVER_MARKUP_YES,
+       EV_ANNOTATION_OVER_MARKUP_NOT
+} EvAnnotationsOverMarkup;
+
 typedef struct _EvDocumentAnnotations          EvDocumentAnnotations;
 typedef struct _EvDocumentAnnotationsInterface EvDocumentAnnotationsInterface;
 
@@ -85,6 +92,10 @@ struct _EvDocumentAnnotationsInterface
                                                 EvAnnotationsSaveMask  mask);
        void           (* remove_annotation)    (EvDocumentAnnotations *document_annots,
                                                 EvAnnotation          *annot);
+       EvAnnotationsOverMarkup (* over_markup) (EvDocumentAnnotations *document_annots,
+                                                EvAnnotation          *annot,
+                                                gdouble                 x,
+                                                gdouble                 y);
 };
 
 GType          ev_document_annotations_get_type             (void) G_GNUC_CONST;
@@ -102,6 +113,10 @@ void           ev_document_annotations_save_annotation      (EvDocumentAnnotatio
                                                             EvAnnotationsSaveMask  mask);
 gboolean       ev_document_annotations_can_add_annotation    (EvDocumentAnnotations *document_annots);
 gboolean       ev_document_annotations_can_remove_annotation (EvDocumentAnnotations *document_annots);
+EvAnnotationsOverMarkup ev_document_annotations_over_markup  (EvDocumentAnnotations *document_annots,
+                                                             EvAnnotation          *annot,
+                                                             gdouble                x,
+                                                             gdouble                y);
 
 G_END_DECLS
 
diff --git a/libview/ev-view.c b/libview/ev-view.c
index 33a7af2a..9c307a00 100644
--- a/libview/ev-view.c
+++ b/libview/ev-view.c
@@ -3318,6 +3318,30 @@ hide_annotation_windows (EvView *view,
        }
 }
 
+static int
+cmp_mapping_area_size (EvMapping *a,
+                      EvMapping *b)
+{
+       gdouble wa, ha, wb, hb;
+
+       wa = a->area.x2 - a->area.x1;
+       ha = a->area.y2 - a->area.y1;
+       wb = b->area.x2 - b->area.x1;
+       hb = b->area.y2 - b->area.y1;
+
+       if (wa == wb) {
+               if (ha == hb)
+                       return 0;
+               return (ha < hb) ? -1 : 1;
+       }
+
+       if (ha == hb) {
+               return (wa < wb) ? -1 : 1;
+       }
+
+       return (wa * ha < wb * hb) ? -1 : 1;
+}
+
 static EvMapping *
 get_annotation_mapping_at_location (EvView *view,
                                    gdouble x,
@@ -3326,8 +3350,14 @@ get_annotation_mapping_at_location (EvView *view,
 {
        gint x_new = 0, y_new = 0;
        EvMappingList *annotations_mapping;
+       EvDocumentAnnotations *doc_annots;
+       EvAnnotation *annot;
+       EvMapping *best;
+       GList *list;
 
-       if (!EV_IS_DOCUMENT_ANNOTATIONS (view->document))
+       doc_annots = EV_DOCUMENT_ANNOTATIONS (view->document);
+
+       if (!doc_annots)
                return NULL;
 
        if (!get_doc_point_from_location (view, x, y, page, &x_new, &y_new))
@@ -3335,10 +3365,33 @@ get_annotation_mapping_at_location (EvView *view,
 
        annotations_mapping = ev_page_cache_get_annot_mapping (view->page_cache, *page);
 
-       if (annotations_mapping)
-               return ev_mapping_list_get (annotations_mapping, x_new, y_new);
+       if (!annotations_mapping)
+               return NULL;
 
-       return NULL;
+       best = NULL;
+       for (list = ev_mapping_list_get_list (annotations_mapping); list; list = list->next) {
+               EvMapping *mapping = list->data;
+
+               if ((x_new >= mapping->area.x1) &&
+                   (y_new >= mapping->area.y1) &&
+                   (x_new <= mapping->area.x2) &&
+                   (y_new <= mapping->area.y2)) {
+
+                       annot = EV_ANNOTATION (mapping->data);
+
+                       if (ev_annotation_get_annotation_type (annot) == EV_ANNOTATION_TYPE_TEXT_MARKUP &&
+                           ev_document_annotations_over_markup (doc_annots, annot, (gdouble) x_new, 
(gdouble) y_new)
+                                                               == EV_ANNOTATION_OVER_MARKUP_NOT)
+                               continue; /* ignore markup annots clicked outside the markup text */
+
+                       /* In case of only one match choose that. Otherwise
+                        * compare the area of the bounding boxes and return the
+                        * smallest element */
+                       if (best == NULL || cmp_mapping_area_size (mapping, best) < 0)
+                               best = mapping;
+               }
+       }
+       return best;
 }
 
 static EvAnnotation *