[lmi-commits] [lmi] master ebfdc8a 3/7: Replace wxDCFontChanger with dc_font_preserver

[Greg Chicares]

branch: master
commit ebfdc8a7cd56ac5d3daa0911c14321b27df1c9f4
Author: Vadim Zeitlin <address@hidden>
Commit: Gregory W. Chicares <address@hidden>

    Replace wxDCFontChanger with dc_font_preserver
    
    The new class is slightly more efficient as it avoids an extra SetFont()
    call but, more importantly, is clearer as we don't actually need to
    change the font in any of the places where wxDCFontChanger was used,
    just to preserve the font currently being used.
---
 pdf_writer_wx.cpp | 35 ++++++++++++++++++++++++++++-------
 1 file changed, 28 insertions(+), 7 deletions(-)

diff --git a/pdf_writer_wx.cpp b/pdf_writer_wx.cpp
index eacf946..0420fcf 100644
--- a/pdf_writer_wx.cpp
+++ b/pdf_writer_wx.cpp
@@ -64,6 +64,29 @@ void DoSetFonts(T& html_object, 
pdf_writer_wx::html_font_sizes const& font_sizes
     html_object.SetFonts("Helvetica", "Courier", font_sizes.data());
 }
 
+// Helper ensuring that the font of the specified DC is restored on scope exit.
+class dc_font_preserver
+{
+  public:
+    explicit dc_font_preserver(wxDC& dc)
+        :dc_   {dc}
+        ,font_ {dc.GetFont()}
+    {
+    }
+
+    ~dc_font_preserver()
+    {
+        dc_.SetFont(font_);
+    }
+
+    dc_font_preserver(dc_font_preserver const&) = delete;
+    dc_font_preserver& operator=(dc_font_preserver const&) = delete;
+
+  private:
+    wxDC&        dc_;
+    wxFont const font_;
+};
+
 } // Unnamed namespace.
 
 pdf_writer_wx::pdf_writer_wx
@@ -239,9 +262,8 @@ int pdf_writer_wx::output_html
 {
     LMI_ASSERT(!save_has_been_called_);
 
-    // We don't really want to change the font, but to preserve the current DC
-    // font which is changed by rendering the HTML contents.
-    wxDCFontChanger preserve_font(pdf_dc_, *wxNORMAL_FONT);
+    // Preserve the current font changed by rendering the HTML contents.
+    dc_font_preserver font_preserver(pdf_dc_);
 
     cell.Layout(width);
     switch(output_mode)
@@ -335,9 +357,8 @@ void pdf_writer_wx::initialize_html_parser(wxHtmlWinParser& 
html_parser)
 
 std::unique_ptr<wxHtmlContainerCell> pdf_writer_wx::parse_html(html::text&& 
html)
 {
-    // We don't really want to change the font, but to preserve the current DC
-    // font which is changed by parsing the HTML contents.
-    wxDCFontChanger preserve_font(pdf_dc_, *wxNORMAL_FONT);
+    // Preserve the current font changed by parsing the HTML contents.
+    dc_font_preserver font_preserver(pdf_dc_);
 
     return std::unique_ptr<wxHtmlContainerCell>
         (static_cast<wxHtmlContainerCell*>
@@ -361,7 +382,7 @@ pdf_writer_wx::make_html_from(wxHtmlCell* cell)
 {
     // Initializing wxHtmlWinParser changes the font of the DC, so
     // ensure that we preserve the original font.
-    wxDCFontChanger preserve_font(writer.dc(), *wxNORMAL_FONT);
+    dc_font_preserver font_preserver(pdf_dc_);
 
     wxHtmlWinParser html_parser;
     initialize_html_parser(html_parser);