fix toUTF8 deprecation

src/dlangui/core/events.d

@@ -24,7 +24,7 @@ private import dlangui.widgets.widget;
 
 private import std.string;
 private import std.conv;
-private import std.utf;
+private import std.utf : toUTF32;
 
 /// Keyboard accelerator (key + modifiers)
 struct Accelerator {

src/dlangui/core/files.d

@@ -425,7 +425,7 @@ RootEntry[] getBookmarkPaths() nothrow
         
         import core.stdc.wchar_ : wcslen;
         import std.exception : enforce;
-        import std.utf : toUTF8, toUTF16z;
+        import std.utf : toUTF16z;
         import std.file : dirEntries, SpanMode;
         import std.string : endsWith;
         

src/dlangui/core/i18n.d

@@ -65,7 +65,7 @@ import dlangui.core.logger;
 import dlangui.core.files;
 import dlangui.graphics.resources;
 private import dlangui.core.linestream;
-private import std.utf;
+private import std.utf : toUTF32;
 private import std.algorithm;
 private import std.string;
 private import std.file;

src/dlangui/core/types.d

@@ -519,3 +519,15 @@ uint parseHexDigit(T)(T ch) pure nothrow {
         return ch - 'A' + 10;
     return uint.max;
 }
+
+/// replacement of deprecated std.utf.toUTF8
+string toUTF8(dstring str) {
+    import std.utf : encode, codeLength, byUTF;
+    char[] buf;
+    buf.length = codeLength!char(str);
+    int pos = 0;
+    foreach(ch; str.byUTF!char) {
+        buf.ptr[pos++] = ch;
+    }
+    return cast(string)buf;
+}

src/dlangui/dialogs/filedlg.d

@@ -41,7 +41,7 @@ import dlangui.dialogs.dialog;
 private import std.algorithm;
 private import std.file;
 private import std.path;
-private import std.utf;
+private import std.utf : toUTF32;
 private import std.string;
 private import std.array;
 private import std.conv : to;

src/dlangui/dialogs/settingsdialog.d

@@ -19,7 +19,7 @@ import dlangui.dialogs.dialog;
 private import std.algorithm;
 private import std.file;
 private import std.path;
-private import std.utf;
+private import std.utf : toUTF32;
 private import std.conv : to;
 private import std.array : split;
 

src/dlangui/dml/parser.d

@@ -31,7 +31,7 @@ import dlangui.widgets.widget;
 import dlangui.widgets.metadata;
 import std.conv : to;
 import std.algorithm : equal, min, max;
-import std.utf : toUTF32, toUTF8;
+import std.utf : toUTF32;
 import std.array : join;
 public import dlangui.dml.annotations;
 public import dlangui.dml.tokenizer;

src/dlangui/dml/tokenizer.d

@@ -4,7 +4,7 @@ import dlangui.core.types;
 import dlangui.core.linestream;
 
 import std.conv : to;
-import std.utf : toUTF32, toUTF8;
+import std.utf : toUTF32;
 import std.algorithm : equal, min, max;
 
 enum TokenType : ushort {
@@ -450,7 +450,7 @@ class Tokenizer {
     }
 
     string getContextSource() {
-        string s = toUTF8(_lineText);
+        string s = toUTF8(cast(dstring)_lineText);
         if (_pos == 0)
             return " near `^^^" ~ s[0..min($,30)] ~ "`";
         if (_pos >= _len)

src/dlangui/package.d

@@ -83,5 +83,5 @@ public {
     // some useful imports from Phobos
     import std.algorithm : equal;
     import std.conv : to;
-    import std.utf : toUTF32, toUTF8;
+    import std.utf : toUTF32;
 }