[vte] ring: Fix image memory leak

[Christian Persch <chpe src gnome org>]

commit cede6dac6bd281ebcf1e259b25079ceafb39ea0b
Author: Christian Persch <chpe src gnome org>
Date:   Tue Dec 1 22:05:58 2020 +0100

    ring: Fix image memory leak
    
    ... and various code correctness and style issues.
    
    Use unique_ptr instead of naked new/delete, and use a std::multimap for
    m_image_by_top_map.
    
    https://gitlab.gnome.org/GNOME/vte/-/issues/255

 src/image.hh |   4 +-
 src/ring.cc  | 179 +++++++++++++++++++++++++++++------------------------------
 src/ring.hh  |  52 +++++++++++------
 src/vte.cc   |   8 +--
 4 files changed, 129 insertions(+), 114 deletions(-)
---
diff --git a/src/image.hh b/src/image.hh
index 5fc031ca..c61c5405 100644
--- a/src/image.hh
+++ b/src/image.hh
@@ -31,7 +31,7 @@ private:
         vte::Freeable<cairo_surface_t> m_surface{};
 
         // Draw/prune priority, must be unique
-        int m_priority;
+        size_t m_priority;
 
         // Image dimensions in pixels
         int m_width_pixels;
@@ -47,7 +47,7 @@ private:
 
 public:
         Image(vte::Freeable<cairo_surface_t> surface,
-              int priority,
+              size_t priority,
               int width_pixels,
               int height_pixels,
               int col,
diff --git a/src/ring.cc b/src/ring.cc
index 27fcec21..3e74c242 100644
--- a/src/ring.cc
+++ b/src/ring.cc
@@ -28,7 +28,7 @@
 
 #ifdef WITH_SIXEL
 
-#include <new>
+#include "cxx-utils.hh"
 
 /* We should be able to hold a single fullscreen 4K image at most.
  * 35MiB equals 3840 * 2160 * 4 plus a little extra. */
@@ -51,10 +51,6 @@ _attrcpy (void *dst, void *src)
 
 using namespace vte::base;
 
-#ifdef WITH_SIXEL
-using namespace vte::image;
-#endif
-
 /*
  * VteRing: A buffer ring
  */
@@ -104,13 +100,6 @@ Ring::Ring(row_t max_rows,
         auto empty_str = g_string_new_len("", 0);
         g_ptr_array_add(m_hyperlinks, empty_str);
 
-#ifdef WITH_SIXEL
-        m_image_by_top_map = new (std::nothrow) std::map<int, Image *>();
-        m_image_priority_map = new (std::nothrow) std::map<int, Image *>();
-        m_next_image_priority = 0;
-        m_image_fast_memory_used = 0;
-#endif
-
        validate();
 }
 
@@ -121,17 +110,6 @@ Ring::~Ring()
 
        g_free (m_array);
 
-#ifdef WITH_SIXEL
-        /* Clear images */
-       auto image_map = m_image_by_top_map;
-
-        for (auto it = image_map->begin (); it != image_map->end (); ++it)
-                delete it->second;
-        image_map->clear();
-        delete m_image_by_top_map;
-        delete m_image_priority_map;
-#endif /* WITH_SIXEL */
-
        if (m_has_streams) {
                g_object_unref (m_attr_stream);
                g_object_unref (m_text_stream);
@@ -230,87 +208,95 @@ Ring::hyperlink_maybe_gc(row_t increment)
 #ifdef WITH_SIXEL
 
 void
-Ring::image_gc_region()
+Ring::image_gc_region() noexcept
 {
         cairo_region_t *region = cairo_region_create();
 
-        for (auto it = m_image_priority_map->rbegin(); it != m_image_priority_map->rend(); ) {
-                Image *image = it->second;
-                cairo_rectangle_int_t r;
-
-                r.x = image->get_left();
-                r.y = image->get_top();
-                r.width = image->get_width();
-                r.height = image->get_height();
+        for (auto rit = m_image_map.rbegin();
+             rit != m_image_map.rend();
+             ) {
+                auto const& image = rit->second;
+                auto const rect = cairo_rectangle_int_t{image->get_left(),
+                                                        image->get_top(),
+                                                        image->get_width(),
+                                                        image->get_height()};
 
-                if (cairo_region_contains_rectangle(region, &r) == CAIRO_REGION_OVERLAP_IN) {
-                        /* Image has been completely overdrawn; delete it */
+                if (cairo_region_contains_rectangle(region, &rect) == CAIRO_REGION_OVERLAP_IN) {
+                        /* vte::image::Image has been completely overdrawn; delete it */
 
                         m_image_fast_memory_used -= image->resource_size();
 
                         /* Apparently this is the cleanest way to erase() with a reverse iterator... */
-                        it = decltype(it){m_image_priority_map->erase(std::next(it).base())};
-                        unlink_image_from_top_map(image);
-                        delete image;
+                        /* Unlink the image from m_image_by_top_map, then erase it from m_image_map */
+                        unlink_image_from_top_map(image.get());
+                        rit = image_map_type::reverse_iterator{m_image_map.erase(std::next(rit).base())};
                         continue;
                 }
 
-                cairo_region_union_rectangle(region, &r);
-                it++;
+                cairo_region_union_rectangle(region, &rect);
+                ++rit;
         }
 
         cairo_region_destroy(region);
 }
 
 void
-Ring::image_gc()
+Ring::image_gc() noexcept
 {
-        while (m_image_fast_memory_used > IMAGE_FAST_MEMORY_USED_MAX
-               || m_image_priority_map->size() > IMAGE_FAST_COUNT_MAX) {
-                if (m_image_priority_map->empty()) {
+        while (m_image_fast_memory_used > IMAGE_FAST_MEMORY_USED_MAX ||
+               m_image_map.size() > IMAGE_FAST_COUNT_MAX) {
+                if (m_image_map.empty()) {
                         /* If this happens, we've miscounted somehow. */
                         break;
                 }
 
-                Image *image = m_image_priority_map->begin()->second;
+                auto& image = m_image_map.begin()->second;
                 m_image_fast_memory_used -= image->resource_size();
-                m_image_priority_map->erase(m_image_priority_map->begin());
-                unlink_image_from_top_map(image);
-                delete image;
+                unlink_image_from_top_map(image.get());
+                m_image_map.erase(m_image_map.begin());
         }
 }
 
 void
-Ring::unlink_image_from_top_map(Image *image)
+Ring::unlink_image_from_top_map(vte::image::Image const* image) noexcept
 {
-        for (auto it = m_image_by_top_map->find(image->get_top()); it != m_image_by_top_map->end(); it++) {
-                Image *cur_image = it->second;
+        auto [begin, end] = m_image_by_top_map.equal_range(image->get_top());
 
-                if (cur_image->get_priority() == image->get_priority()) {
-                        m_image_by_top_map->erase(it);
-                        break;
-                }
+        for (auto it = begin; it != end; ++it) {
+                if (it->second != image)
+                        continue;
+
+                m_image_by_top_map.erase(it);
+                break;
         }
 }
 
 void
-Ring::rebuild_image_top_map()
+Ring::rebuild_image_top_map() /* throws */
 {
-        m_image_by_top_map->clear();
-
-        for (auto it = m_image_priority_map->begin(); it != m_image_priority_map->end(); it++) {
-                Image *image = it->second;
-                m_image_by_top_map->insert(std::make_pair(image->get_top(), image));
+        m_image_by_top_map.clear();
+
+        for (auto it = m_image_map.begin(), end = m_image_map.end();
+             it != end;
+             ++it) {
+                auto const& image = it->second;
+                m_image_by_top_map.emplace(std::piecewise_construct,
+                                           std::forward_as_tuple(image->get_top()),
+                                           std::forward_as_tuple(image.get()));
         }
 }
 
 bool
-Ring::rewrap_images_in_range(std::map<int,Image*>::iterator &it,
-                             size_t text_start_ofs, size_t text_end_ofs, row_t new_row_index)
+Ring::rewrap_images_in_range(Ring::image_by_top_map_type::iterator& it,
+                             size_t text_start_ofs,
+                             size_t text_end_ofs,
+                             row_t new_row_index) noexcept
 {
-        for ( ; it != m_image_by_top_map->end(); it++) {
-                Image *image = it->second;
-                CellTextOffset ofs;
+        for (auto const end = m_image_by_top_map.end();
+             it != end;
+             ++it) {
+                auto const& image = it->second;
+                auto ofs = CellTextOffset{};
 
                 if (!frozen_row_column_to_text_offset(image->get_top(), 0, &ofs))
                         return false;
@@ -722,10 +708,6 @@ Ring::reset_streams(row_t position)
 Ring::row_t
 Ring::reset()
 {
-#ifdef WITH_SIXEL
-        auto image_map = m_image_by_top_map;
-#endif
-
         _vte_debug_print (VTE_DEBUG_RING, "Reseting the ring at %lu.\n", m_end);
 
         reset_streams(m_end);
@@ -733,11 +715,8 @@ Ring::reset()
         m_cached_row_num = (row_t)-1;
 
 #ifdef WITH_SIXEL
-        /* Clear images */
-        for (auto it = image_map->begin (); it != image_map->end (); ++it)
-                delete it->second;
-        image_map->clear();
-        m_image_priority_map->clear();
+        m_image_by_top_map.clear();
+        m_image_map.clear();
         m_next_image_priority = 0;
         m_image_fast_memory_used = 0;
 #endif
@@ -1326,7 +1305,7 @@ Ring::rewrap(column_t columns,
        gsize attr_offset;
        gsize old_ring_end;
 #ifdef WITH_SIXEL
-       auto image_it = m_image_by_top_map->begin();
+       auto image_it = m_image_by_top_map.begin();
 #endif
 
        if (G_UNLIKELY(length() == 0))
@@ -1464,7 +1443,10 @@ Ring::rewrap(column_t columns,
                                                }
 
 #ifdef WITH_SIXEL
-                                               if (!rewrap_images_in_range(image_it, 
new_record.text_start_offset, text_offset, new_row_index))
+                                               if (!rewrap_images_in_range(image_it,
+                                                                            new_record.text_start_offset,
+                                                                            text_offset,
+                                                                            new_row_index))
                                                        goto err;
 #endif
 
@@ -1518,7 +1500,10 @@ Ring::rewrap(column_t columns,
                }
 
 #ifdef WITH_SIXEL
-               if (!rewrap_images_in_range(image_it, new_record.text_start_offset, 
paragraph_end_text_offset, new_row_index))
+               if (!rewrap_images_in_range(image_it,
+                                            new_record.text_start_offset,
+                                            paragraph_end_text_offset,
+                                            new_row_index))
                        goto err;
 #endif
 
@@ -1555,7 +1540,11 @@ Ring::rewrap(column_t columns,
        g_free(new_markers);
 
 #ifdef WITH_SIXEL
-       rebuild_image_top_map();
+        try {
+                rebuild_image_top_map();
+        } catch (...) {
+                vte::log_exception();
+        }
 #endif
 
        _vte_debug_print(VTE_DEBUG_RING, "Ring after rewrapping:\n");
@@ -1667,8 +1656,8 @@ Ring::write_contents(GOutputStream* stream,
 /**
  * Ring::append_image:
  * @surface: A Cairo surface object
- * @pixelwidth: Image width in pixels
- * @pixelheight: Image height in pixels
+ * @pixelwidth: vte::image::Image width in pixels
+ * @pixelheight: vte::image::Image height in pixels
  * @left: Left position of image in cell units
  * @top: Top position of image in cell units
  * @cell_width: Width of image in cell units
@@ -1685,18 +1674,28 @@ Ring::append_image(vte::Freeable<cairo_surface_t> surface,
                    long cell_width,
                    long cell_height) /* throws */
 {
-        Image *image;
-
-        image = new (std::nothrow) Image(std::move(surface),
-                                         m_next_image_priority++,
-                                          pixelwidth, pixelheight,
-                                         left, top,
-                                         cell_width, cell_height);
-        if (!image)
+        auto const priority = m_next_image_priority;
+        auto [it, success] = m_image_map.try_emplace
+                (priority, // key
+                 std::make_unique<vte::image::Image>(std::move(surface),
+                                                     priority,
+                                                     pixelwidth,
+                                                     pixelheight,
+                                                     left,
+                                                     top,
+                                                     cell_width,
+                                                     cell_height));
+        if (!success)
                 return;
 
-        m_image_by_top_map->insert (std::make_pair (image->get_top (), image));
-        m_image_priority_map->insert (std::make_pair (image->get_priority (), image));
+        ++m_next_image_priority;
+
+        auto const& image = it->second;
+
+        m_image_by_top_map.emplace(std::piecewise_construct,
+                                   std::forward_as_tuple(image->get_top()),
+                                   std::forward_as_tuple(image.get()));
+
         m_image_fast_memory_used += image->resource_size ();
 
         image_gc_region();
diff --git a/src/ring.hh b/src/ring.hh
index 281ec7c0..acd7a57d 100644
--- a/src/ring.hh
+++ b/src/ring.hh
@@ -32,6 +32,7 @@
 #include "cairo-glue.hh"
 #include "image.hh"
 #include <map>
+#include <memory>
 #endif
 
 #include <type_traits>
@@ -104,15 +105,6 @@ public:
                             GCancellable* cancellable,
                             GError** error);
 
-#ifdef WITH_SIXEL
-        void append_image (vte::Freeable<cairo_surface_t> surface,
-                           gint pixelwidth, gint pixelheight,
-                           glong left, glong top,
-                           glong cell_width, glong cell_height) /* throws */;
-        std::map<gint, vte::image::Image *> *m_image_by_top_map;
-        std::map<int, vte::image::Image *> *m_image_priority_map;
-#endif
-
 private:
 
         #ifdef VTE_DEBUG
@@ -243,17 +235,41 @@ private:
         row_t m_hyperlink_maybe_gc_counter{0};  /* Do a GC when it reaches 65536. */
 
 #ifdef WITH_SIXEL
-        /* Image bookkeeping */
 
-        void image_gc();
-        void image_gc_region();
-        void unlink_image_from_top_map(vte::image::Image *image);
-        void rebuild_image_top_map();
-        bool rewrap_images_in_range(std::map<int,vte::image::Image*>::iterator &it,
-                                    size_t text_start_ofs, size_t text_end_ofs, row_t new_row_index);
+private:
+        size_t m_next_image_priority{0};
+        size_t m_image_fast_memory_used{0};
+
+        /* m_image_priority_map stores the Image. key is the priority of the image. */
+        using image_map_type = std::map<size_t, std::unique_ptr<vte::image::Image>>;
+        image_map_type m_image_map{};
+
+        /* m_image_by_top_map stores only an iterator to the Image in m_image_priority_map;
+         * key is the top row of the image.
+         */
+        using image_by_top_map_type = std::multimap<row_t, vte::image::Image*>;
+        image_by_top_map_type m_image_by_top_map{};
+
+        void image_gc() noexcept;
+        void image_gc_region() noexcept;
+        void unlink_image_from_top_map(vte::image::Image const* image) noexcept;
+        void rebuild_image_top_map() /* throws */;
+        bool rewrap_images_in_range(image_by_top_map_type::iterator& it,
+                                    size_t text_start_ofs,
+                                    size_t text_end_ofs,
+                                    row_t new_row_index) noexcept;
+
+public:
+        auto const& image_map() const noexcept { return m_image_map; }
+
+        void append_image(vte::Freeable<cairo_surface_t> surface,
+                          int pixelwidth,
+                          int pixelheight,
+                          long left,
+                          long top,
+                          long cell_width,
+                          long cell_height) /* throws */;
 
-        int m_next_image_priority;
-        unsigned int m_image_fast_memory_used;
 #endif /* WITH_SIXEL */
 };
 
diff --git a/src/vte.cc b/src/vte.cc
index f32c8632..b5df3d24 100644
--- a/src/vte.cc
+++ b/src/vte.cc
@@ -9200,10 +9200,10 @@ Terminal::widget_draw(cairo_t *cr)
        if (m_images_enabled) {
                vte::grid::row_t top_row = first_displayed_row();
                vte::grid::row_t bottom_row = last_displayed_row();
-               auto image_map = ring->m_image_priority_map;
-               auto it = image_map->begin ();
-               for (; it != image_map->end (); ++it) {
-                       vte::image::Image *image = it->second;
+                auto const& image_map = ring->image_map();
+                auto const image_map_end = image_map.end();
+                for (auto it = image_map.begin(); it != image_map_end; ++it) {
+                        auto const& image = it->second;
 
                         if (image->get_bottom() < top_row ||
                             image->get_top() > bottom_row)