Issue #96: PDF4QT crashes when I open PDF

CMakeLists.txt

@@ -104,6 +104,18 @@ option(PDF4QT_INSTALL_TO_USR "Install to usr directory" ON)
 if(PDF4QT_LINUX)
     set(PDF4QT_INSTALL_LIB_DIR_IMPL lib)
     set(PDF4QT_INSTALL_BIN_DIR_IMPL bin)
+
+    # Check if VCPKG_OVERLAY_PORTS is set as an environment variable or a CMake argument
+    if(NOT DEFINED ENV{VCPKG_OVERLAY_PORTS} AND NOT DEFINED VCPKG_OVERLAY_PORTS)
+        message(WARNING "The VCPKG_OVERLAY_PORTS variable is not set! Application can crash in Open/Save dialog due to incompatible LIBPNG.")
+    else()
+        set(VCPKG_OVERLAY_PORTS_VALUE "$ENV{VCPKG_OVERLAY_PORTS}")
+        if(DEFINED VCPKG_OVERLAY_PORTS)
+            set(VCPKG_OVERLAY_PORTS_VALUE "${VCPKG_OVERLAY_PORTS}")
+        endif()
+        message(STATUS "The VCPKG_OVERLAY_PORTS variable is set to: ${VCPKG_OVERLAY_PORTS_VALUE}")
+    endif()
+
 else()
     set(PDF4QT_INSTALL_LIB_DIR_IMPL bin)
     set(PDF4QT_INSTALL_BIN_DIR_IMPL bin)

README.md

@@ -126,6 +126,8 @@ On Linux, a GCC version >= 8 should work, altough we tested it with GCC 11.
 
     For a debug build, append `-DCMAKE_BUILD_TYPE=Debug`.
 
+    It is recommended to set the VCPKG_OVERLAY_PORTS variable to 'PDF4QT/vcpkg/overlays' to prevent crashes due to the incompatible LIBPNG library on some Linux systems.
+
     2.3 Build
 
         cmake --build build
@@ -154,7 +156,8 @@ CMake can prepare a Wix project to create a *.msi installer package.
 | `PDF4QT_INSTALL_PREPARE_WIX_INSTALLER` | Windows  |Prepare .msi installator using Wix installer              |
 | `PDF4QT_INSTALL_DEPENDENCIES`          | Any      |Install dependent libraries into installation directory   |
 | `PDF4QT_INSTALL_QT_DEPENDENCIES`       | Any      |Install Qt dependent libraries into installation directory|
-
+| `VCPKG_OVERLAY_PORTS`                  | Linux    |Set it to prevent crashes with incompatible libpng library|
+ 
 Following important variables should be set or checked before any attempt to compile this project:
 
 |                  Variable              | Platform |     Description                                          |

vcpkg/overlays/libpng/portfile.cmake

@@ -0,0 +1 @@
+set(VCPKG_POLICY_EMPTY_PACKAGE enabled)

vcpkg/overlays/libpng/vcpkg.json

@@ -0,0 +1,5 @@
+{
+    "name": "libpng",
+    "version": "1.0.0",
+    "port-version": 0
+}