Graphics preview in parallel

diff --git a/src/support/ForkedCalls.cpp b/src/support/ForkedCalls.cpp
index 054290d0dd..539bf301db 100644
--- a/src/support/ForkedCalls.cpp
+++ b/src/support/ForkedCalls.cpp
@@ -443,18 +443,19 @@ typedef pair<string, ForkedCall::sigPtr> Process;
 /// in-progress queue
 static queue<Process> callQueue_;
 
-/// flag whether queue is running
-static bool running_ = false;
+/// Max threads consuming the conversion chain for graphics preview
+static int const MAX_RUNNING = 4;
+
+/// Current threads running
+static int running_count_ = 0;
 
 ///
-void startCaller();
-///
-void stopCaller();
+void callNext();
 ///
 void callback(pid_t, int);
 
-/** Add a process to the queue. Processes are forked sequentially
- *  only one is running at a time.
+/** Add a process to the queue. Up to MAX_RUNNING processes are
+ *  forked in parallel; the remainder wait for a slot to free up.
  *  Connect to the returned signal and you'll be informed when
  *  the process has ended.
  */
@@ -463,8 +464,10 @@ ForkedCall::sigPtr add(string const & process)
 	ForkedCall::sigPtr ptr;
 	ptr.reset(new ForkedCall::sig);
 	callQueue_.push(Process(process, ptr));
-	if (!running_)
-		startCaller();
+	if (running_count_ == 0)
+		LYXERR(Debug::GRAPHICS, "ForkedCallQueue: waking up");
+	while (running_count_ < MAX_RUNNING && !callQueue_.empty())
+		callNext();
 	return ptr;
 }
 
@@ -477,6 +480,7 @@ void callNext()
 	callQueue_.pop();
 	// Bind our chain caller
 	pro.second->connect(callback);
+	++running_count_;
 	ForkedCall call;
 	//If we fail to fork the process, then emit the signal
 	//to tell the outside world that it failed.
@@ -487,31 +491,17 @@ void callNext()
 
 void callback(pid_t, int)
 {
-	if (callQueue_.empty())
-		stopCaller();
-	else
+	--running_count_;
+	while (running_count_ < MAX_RUNNING && !callQueue_.empty())
 		callNext();
-}
-
-
-void startCaller()
-{
-	LYXERR(Debug::GRAPHICS, "ForkedCallQueue: waking up");
-	running_ = true ;
-	callNext();
-}
-
-
-void stopCaller()
-{
-	running_ = false ;
-	LYXERR(Debug::GRAPHICS, "ForkedCallQueue: I'm going to sleep");
+	if (running_count_ == 0 && callQueue_.empty())
+		LYXERR(Debug::GRAPHICS, "ForkedCallQueue: I'm going to sleep");
 }
 
 
 bool running()
 {
-	return running_;
+	return running_count_ > 0;
 }
 
 } // namespace ForkedCallQueue

diff --git a/src/Buffer.cpp b/src/Buffer.cpp
index 8122a05843..1f4e139330 100644
--- a/src/Buffer.cpp
+++ b/src/Buffer.cpp
@@ -70,6 +70,7 @@
 #include "xml.h"
 
 #include "insets/InsetBranch.h"
+#include "insets/InsetGraphics.h"
 #include "insets/InsetInclude.h"
 #include "insets/InsetText.h"
 
@@ -2888,6 +2889,10 @@ bool Buffer::getStatus(FuncRequest const & cmd, FuncStatus & flag) const
 		enable = (d->preview_file_).exists() && !(d->preview_file_).isFileEmpty();
 		break;
 
+	case LFUN_BUFFER_LOAD_GRAPHICS:
+		enable = true;
+		break;
+
 	case LFUN_CHANGES_TRACK:
 		flag.setEnabled(true);
 		flag.setOnOff(params().track_changes);
@@ -3163,6 +3168,24 @@ void Buffer::dispatch(FuncRequest const & func, DispatchResult & dr)
 			dr.setMessage(_("Error viewing the output file."));
 		break;
 
+	case LFUN_BUFFER_LOAD_GRAPHICS: {
+		ListOfBuffers bufs = getDescendants();
+		bufs.push_front(this);
+		int counted = 0;
+		for (Buffer * b : bufs) {
+			InsetIterator it = begin(b->inset());
+			InsetIterator const itend = end(b->inset());
+			for (; it != itend; ++it) {
+				if (it->lyxCode() == GRAPHICS_CODE) {
+					static_cast<InsetGraphics const &>(*it).preload();
+					++counted;
+				}
+			}
+		}
+		//dr.setMessage(bformat(_("Queued %1$d image(s) for preview."), counted));
+		break;
+	}
+
 	case LFUN_CHANGES_TRACK:
 		if (params().save_transient_properties)
 			undo().recordUndoBufferParams();
diff --git a/src/FuncCode.h b/src/FuncCode.h
index 0a56683779..5c3259dd68 100644
--- a/src/FuncCode.h
+++ b/src/FuncCode.h
@@ -461,6 +461,7 @@ enum FuncCode
 	LFUN_SEPARATOR_INSERT,          // ef 20140502
 	LFUN_SERVER_GET_STATISTICS,     // brokenclock 20141010
 	LFUN_BUFFER_VIEW_CACHE,         // skostysh 20150401
+	LFUN_BUFFER_LOAD_GRAPHICS,      // ps 20260623
 	// 360
 	LFUN_BUFFER_MOVE_NEXT,          // skostysh 20150408
 	LFUN_BUFFER_MOVE_PREVIOUS,      // skostysh 20150408
diff --git a/src/LyXAction.cpp b/src/LyXAction.cpp
index 0e0826ead4..3da6433db2 100644
--- a/src/LyXAction.cpp
+++ b/src/LyXAction.cpp
@@ -904,6 +904,16 @@ void LyXAction::init()
  */
 		{ LFUN_BUFFER_VIEW_CACHE, "buffer-view-cache", ReadOnly, Buffer },
 
+/*!
+ * \var lyx::FuncCode lyx::LFUN_BUFFER_LOAD_GRAPHICS
+ * \li Action: Start preview conversion for every image in the current buffer/childern, 
+               instead of waiting for each image to be scrolled into view.
+ * \li Syntax: buffer-load-graphics
+ * \li Origin: ps, 23 Jun 2026
+ * \endvar
+ */
+		{ LFUN_BUFFER_LOAD_GRAPHICS, "buffer-load-graphics", ReadOnly, Buffer },
+
 /*!
  * \var lyx::FuncCode lyx::LFUN_BUFFER_WRITE
  * \li Action: Saves the current buffer.
diff --git a/src/insets/InsetGraphics.cpp b/src/insets/InsetGraphics.cpp
index 0ca24e0488..c087533905 100644
--- a/src/insets/InsetGraphics.cpp
+++ b/src/insets/InsetGraphics.cpp
@@ -1157,6 +1157,13 @@ InsetGraphicsParams const & InsetGraphics::params() const
 }
 
 
+void InsetGraphics::preload() const
+{
+	if (graphic_)
+		graphic_->preload();
+}
+
+
 void InsetGraphics::editGraphics(InsetGraphicsParams const & p) const
 {
 	theFormats().edit(buffer(), p.filename,
diff --git a/src/insets/InsetGraphics.h b/src/insets/InsetGraphics.h
index 95289832cb..7f7cb2e81d 100644
--- a/src/insets/InsetGraphics.h
+++ b/src/insets/InsetGraphics.h
@@ -91,6 +91,8 @@ public:
 	docstring layoutName() const override { return from_ascii("Graphics"); }
 	/// Get the inset parameters, used by the GUIndependent dialog.
 	InsetGraphicsParams const & params() const;
+	/// Force preview generation now (skip the wait-for-paint).
+	void preload() const;
 
 	///
 	int topOffset(BufferView const *) const override { return 0; }
diff --git a/src/insets/RenderGraphic.cpp b/src/insets/RenderGraphic.cpp
index 67d44e1bb4..5f88372953 100644
--- a/src/insets/RenderGraphic.cpp
+++ b/src/insets/RenderGraphic.cpp
@@ -51,6 +51,7 @@ RenderBase * RenderGraphic::clone(Inset const * inset) const
 	return new RenderGraphic(*this, inset);
 }
 
+
 void RenderGraphic::reload() const
 {
 	loader_.reload();
@@ -132,6 +133,17 @@ bool readyToDisplay(graphics::Loader const & loader)
 } // namespace
 
 
+void RenderGraphic::preload() const
+{
+	if (!displayGraphic(params_))
+		return;
+	// ErrorConverting is included so we retry failed conversions.
+	if (loader_.status() == graphics::WaitingToLoad
+	    || loader_.status() == graphics::ErrorConverting)
+		loader_.startLoading();
+}
+
+
 void RenderGraphic::metrics(MetricsInfo & mi, Dimension & dim) const
 {
 	if (displayGraphic(params_)) {
diff --git a/src/insets/RenderGraphic.h b/src/insets/RenderGraphic.h
index fc631a0c7a..2b175008a3 100644
--- a/src/insets/RenderGraphic.h
+++ b/src/insets/RenderGraphic.h
@@ -35,6 +35,8 @@ public:
 
 	/// Refresh the info about which file to display and how to display it.
 	void update(graphics::Params const & params);
+	/// Trigger conversion, no-op if the image is already loading, loaded.
+	void preload() const;
 	/// Reloads the image if necessary
 	void reload() const;