[LyX/master] Regularly check if graphics is modified when visible on screen (#10596)

[Guillaume Munch]

commit ad16347b087943741eaca30cc048e1aa32ad57c0
Author: Guillaume Munch <g...@lyx.org>
Date:   Sun Mar 19 14:41:54 2017 +0100

    Regularly check if graphics is modified when visible on screen (#10596)
    
    In case one cannot rely on QFileSystemWatcher.
    
    see https://www.mail-archive.com/lyx-devel@lists.lyx.org/msg199112.html
---
 src/graphics/GraphicsCacheItem.cpp |   12 ++++++++++--
 src/graphics/GraphicsCacheItem.h   |    2 ++
 src/graphics/GraphicsLoader.cpp    |    9 +++++++++
 src/graphics/GraphicsLoader.h      |    2 ++
 src/insets/RenderGraphic.cpp       |    1 +
 5 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/graphics/GraphicsCacheItem.cpp 
b/src/graphics/GraphicsCacheItem.cpp
index 0bd3779..4ed496a 100644
--- a/src/graphics/GraphicsCacheItem.cpp
+++ b/src/graphics/GraphicsCacheItem.cpp
@@ -99,7 +99,7 @@ public:
        /// The document filename this graphic item belongs to
        FileName const & doc_file_;
        ///
-       FileMonitorPtr monitor_;
+       ActiveFileMonitorPtr monitor_;
 
        /// Is the file compressed?
        bool zipped_;
@@ -179,6 +179,14 @@ bool CacheItem::monitoring() const
 }
 
 
+void CacheItem::checkModifiedAsync() const
+{
+       if (!pimpl_->monitor_)
+               return;
+       pimpl_->monitor_->checkModifiedAsync();
+}
+
+
 Image const * CacheItem::image() const
 {
        return pimpl_->image_.get();
@@ -214,7 +222,7 @@ void CacheItem::Impl::startMonitor()
 {
        if (monitor_)
                return;
-       monitor_ = FileSystemWatcher::monitor(filename_);
+       monitor_ = FileSystemWatcher::activeMonitor(filename_);
        monitor_->connect([=](){ startLoading(); });
 }
 
diff --git a/src/graphics/GraphicsCacheItem.h b/src/graphics/GraphicsCacheItem.h
index b6d7d41..9cee2b8 100644
--- a/src/graphics/GraphicsCacheItem.h
+++ b/src/graphics/GraphicsCacheItem.h
@@ -66,6 +66,8 @@ public:
        void startMonitoring() const;
        ///
        bool monitoring() const;
+       /// perform a modification check asynchronously
+       void checkModifiedAsync() const;
 
        /** Get the image associated with filename().
         *  If the image is not yet loaded, returns 0.
diff --git a/src/graphics/GraphicsLoader.cpp b/src/graphics/GraphicsLoader.cpp
index 617ce24..26b4e57 100644
--- a/src/graphics/GraphicsLoader.cpp
+++ b/src/graphics/GraphicsLoader.cpp
@@ -328,6 +328,15 @@ bool Loader::monitoring() const
 }
 
 
+void Loader::checkModifiedAsync() const
+{
+       if (!pimpl_->cached_item_)
+               return;
+
+       pimpl_->cached_item_->checkModifiedAsync();
+}
+
+
 FileName const & Loader::filename() const
 {
        static FileName const empty;
diff --git a/src/graphics/GraphicsLoader.h b/src/graphics/GraphicsLoader.h
index 0b58857..62ea303 100644
--- a/src/graphics/GraphicsLoader.h
+++ b/src/graphics/GraphicsLoader.h
@@ -81,6 +81,8 @@ public:
        void startMonitoring() const;
        ///
        bool monitoring() const;
+       ///
+       void checkModifiedAsync() const;
 
        /// How far have we got in loading the image?
        ImageStatus status() const;
diff --git a/src/insets/RenderGraphic.cpp b/src/insets/RenderGraphic.cpp
index 7ab14cb..d48e477 100644
--- a/src/insets/RenderGraphic.cpp
+++ b/src/insets/RenderGraphic.cpp
@@ -142,6 +142,7 @@ void RenderGraphic::metrics(MetricsInfo & mi, Dimension & 
dim) const
                        loader_.startLoading();
                if (!loader_.monitoring())
                        loader_.startMonitoring();
+               loader_.checkModifiedAsync();
        }
 
        bool const image_ready = displayGraphic(params_) && 
readyToDisplay(loader_);