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

@@ -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 */

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;
+}

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
 

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 *