Improve Linux file dialog support

Adds support for multi selection, filtering and initial folder for both zenity and kdialog. kdialog is also preferred over zenity when KDE is detected.

Source/Engine/Platform/Base/FileSystemBase.h

@@ -50,11 +50,16 @@ DECLARE_SCRIPTING_TYPE_MINIMAL(FileSystemBase);
     /// </summary>
     /// <param name="parentWindow">The parent window or null.</param>
     /// <param name="initialDirectory">The initial directory.</param>
-    /// <param name="filter">The custom filter.</param>
+    /// <param name="filter">The file filter string as null-terminated pairs of name and list of extensions. Multiple file extensions must be separated with semicolon.</param>
     /// <param name="multiSelect">True if allow multiple files to be selected, otherwise use single-file mode.</param>
     /// <param name="title">The dialog title.</param>
     /// <param name="filenames">The output names of the files picked by the user.</param>
     /// <returns>True if failed, otherwise false.</returns>
+    /// <remarks>
+    /// Example file filters:
+    ///    "All Files\0*.*"
+    ///    "All Files\0*.*\0Image Files\0*.png;*.jpg"
+    /// </remarks>
     API_FUNCTION() static bool ShowOpenFileDialog(Window* parentWindow, const StringView& initialDirectory, const StringView& filter, bool multiSelect, const StringView& title, API_PARAM(Out) Array<String, HeapAllocation>& filenames);
 
     /// <summary>
@@ -62,11 +67,16 @@ DECLARE_SCRIPTING_TYPE_MINIMAL(FileSystemBase);
     /// </summary>
     /// <param name="parentWindow">The parent window.</param>
     /// <param name="initialDirectory">The initial directory.</param>
-    /// <param name="filter">The filter.</param>
+    /// <param name="filter">The file filter string as null-terminated pairs of name and list of extensions. Multiple file extensions must be separated with semicolon.</param>
     /// <param name="multiSelect">True if allow multiple files to be selected, otherwise use single-file mode.</param>
     /// <param name="title">The title.</param>
     /// <param name="filenames">The output names of the files picked by the user.</param>
     /// <returns>True if failed, otherwise false.</returns>
+    /// <remarks>
+    /// Example file filters:
+    ///    "All Files\0*.*"
+    ///    "All Files\0*.*\0Image Files\0*.png;*.jpg"
+    /// </remarks>
     API_FUNCTION() static bool ShowSaveFileDialog(Window* parentWindow, const StringView& initialDirectory, const StringView& filter, bool multiSelect, const StringView& title, API_PARAM(Out) Array<String, HeapAllocation>& filenames);
 
     /// <summary>

Source/Engine/Platform/Base/StringUtilsBase.cpp

@@ -528,4 +528,17 @@ String StringUtils::ToString(double value)
     return String::Format(TEXT("{}"), value);
 }
 
+String StringUtils::GetZZString(const Char* str)
+{
+    const Char* end = str;
+    while (*end != '\0')
+    {
+        end++;
+        if (*end == '\0')
+            end++;
+    }
+    const int len = end - str;
+    return String(str, len);
+}
+
 #undef STRING_UTILS_ITOSTR_BUFFER_SIZE

Source/Engine/Platform/Linux/LinuxFileSystem.cpp

@@ -4,7 +4,9 @@
 
 #include "LinuxFileSystem.h"
 #include "Engine/Platform/File.h"
+#include "Engine/Platform/StringUtils.h"
 #include "Engine/Core/Types/String.h"
+#include "Engine/Core/Types/StringBuilder.h"
 #include "Engine/Core/Types/StringView.h"
 #include "Engine/Core/Types/TimeSpan.h"
 #include "Engine/Core/Math/Math.h"
@@ -27,20 +29,38 @@ bool LinuxFileSystem::ShowOpenFileDialog(Window* parentWindow, const StringView&
 {
     const StringAsANSI<> initialDirectoryAnsi(*initialDirectory, initialDirectory.Length());
     const StringAsANSI<> titleAnsi(*title, title.Length());
+    const char* initDir = initialDirectory.HasChars() ? initialDirectoryAnsi.Get() : ".";
     char cmd[2048];
-    if (FileSystem::FileExists(TEXT("/usr/bin/zenity")))
+    String xdgCurrentDesktop;
+    StringBuilder fileFilter;
+    Array<String> fileFilterEntries;
+    Platform::GetEnvironmentVariable(TEXT("XDG_CURRENT_DESKTOP"), xdgCurrentDesktop);
+    StringUtils::GetZZString(filter.Get()).Split('\0', fileFilterEntries);
+
+    const bool zenitySupported = FileSystem::FileExists(TEXT("/usr/bin/zenity"));
+    const bool kdialogSupported = FileSystem::FileExists(TEXT("/usr/bin/kdialog"));
+    if (zenitySupported && (xdgCurrentDesktop != TEXT("KDE") || !kdialogSupported)) // Prefer kdialog when running on KDE
     {
-        // TODO: initialDirectory support
+        for (int32 i = 1; i < fileFilterEntries.Count(); i += 2)
-        // TODO: multiSelect support
+        {
-        // TODO: filter support
+            String extensions(fileFilterEntries[i]);
-        sprintf(cmd, "/usr/bin/zenity --modal --file-selection --title=\"%s\" ", titleAnsi.Get());
+            fileFilterEntries[i].Replace(TEXT(";"), TEXT(" "));
+            fileFilter.Append(String::Format(TEXT("{0}--file-filter=\"{1}|{2}\""), i > 1 ? TEXT(" ") : TEXT(""), fileFilterEntries[i-1].Get(), extensions.Get()));
+        }
+
+        sprintf(cmd, "/usr/bin/zenity --modal --file-selection %s--filename=\"%s\" --title=\"%s\" %s ", multiSelect ? "--multiple --separator=$'\n' " : " ", initDir, titleAnsi.Get(), fileFilter.ToStringView().ToStringAnsi().GetText());
     }
-    else if (FileSystem::FileExists(TEXT("/usr/bin/kdialog")))
+    else if (kdialogSupported)
     {
-        // TODO: multiSelect support
+        for (int32 i = 1; i < fileFilterEntries.Count(); i += 2)
-        // TODO: filter support
+        {
-        const char* initDir = initialDirectory.HasChars() ? initialDirectoryAnsi.Get() : ".";
+            String extensions(fileFilterEntries[i]);
-        sprintf(cmd, "/usr/bin/kdialog --getopenfilename \"%s\" --title \"%s\" ", initDir, titleAnsi.Get());
+            fileFilterEntries[i].Replace(TEXT(";"), TEXT(" "));
+            fileFilter.Append(String::Format(TEXT("{0}\"{1}({2})\""), i > 1 ? TEXT(" ") : TEXT(""), fileFilterEntries[i-1].Get(), extensions.Get()));
+        }
+        fileFilter.Append(String::Format(TEXT("{0}\"{1}({2})\""), TEXT(" "), TEXT("many things"), TEXT("*.png *.jpg")));
+
+        sprintf(cmd, "/usr/bin/kdialog --getopenfilename %s--title \"%s\" \"%s\" %s ", multiSelect ? "--multiple --separate-output " : " ", titleAnsi.Get(), initDir, fileFilter.ToStringView().ToStringAnsi().GetText());
     }
     else
     {

Source/Engine/Platform/StringUtils.h

@@ -438,6 +438,13 @@ public:
     static String ToString(uint64 value);
     static String ToString(float value);
     static String ToString(double value);
+
+public:
+
+    // Returns the String to double null-terminated string
+    // @param str Double null-terminated string
+    // @return Double null-terminated String
+    static String GetZZString(const Char* str);
 };
 
 inline uint32 GetHash(const char* key)