Introduce HiDPI + rescaling support for the X11 platform (+ partial support for WIN32)

Corresponds to STR #3320
1) HiDPI support consists in detecting the adequate scaling factor for the screen on which
FLTK maps a window, and scaling all FLTK units by this factor. FLTK tries to detect the correct
value of this factor at startup (see more details below). Environment variable
FLTK_SCALING_FACTOR can also be used to set this value.
2) Rescaling support consists in changing the scaling factor of all FLTK windows
in reply to ctrl/+/-/0/ keystrokes.

More details for the various platforms :

- X11: Support is very advanced. Some details need still to be improved.
Automatic detection of the correct starting value of the scaling factor works well
with the gnome desktop. The present code contains no support for this on
other desktops.  FLTK_SCALING_FACTOR provides a workaround.

-WIN32: Support is incomplete at this point, although many test
applications have partial or complete HiDPI and scaling support.
The current value of the system's scaling factor is correctly detected
at application startup. Apps respond to changes of this value in real time.
Support needs to define the FLTK_HIDPI_SUPPORT preprocessor variable
at compile time. This way, standard builds produce a code with the
default WIN32 HiDPI support, that is, where all graphics goes to an internal
buffer that gets enlarged by the system and then mapped to the HiDPI
display. To experiment with (or develop) the new HiDPI support requires
a modified build procedure in which  FLTK_HIDPI_SUPPORT is defined
at compile time. When the support will be complete, the requirement for the
definition of this preprocessor variable will be removed. The present commit
contains support for a single scaling factor. Eventually, per-screen scaling
factors should be implemented, as done for X11.

- MacOS: this commit does not give new HiDPI for this platform.
Eventually, window rescaling in reply to command/+/-/0/ is desirable.
Per-screen scaling factor makes no sense on this platform because
the OS itself takes care of the difference between the resolutions of
traditional and retina displays.


git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12239 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

1 files changed, 92 insertions, 63 deletions

diff --git a/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_font_xft.cxx b/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_font_xft.cxx
index 48771d0a2..a2c655455 100644
--- a/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_font_xft.cxx
+++ b/src/drivers/Xlib/Fl_Xlib_Graphics_Driver_font_xft.cxx
@@ -3,7 +3,7 @@
 //
 // More font utilities for the Fast Light Tool Kit (FLTK).
 //
-// Copyright 1998-2016 by Bill Spitzak and others.
+// Copyright 1998-2017 by Bill Spitzak and others.
 //
 // This library is free software. Distribution and use rights are outlined in
 // the file "COPYING" which should have been included with this file.  If this
@@ -125,6 +125,30 @@ static Fl_Fontdesc built_in_table[] = {
 
 Fl_Fontdesc* fl_fonts = built_in_table;
 
+Fl_Fontsize Fl_Xlib_Graphics_Driver::size_unscaled() {
+  return (Fl_Fontsize)(size_);
+}
+
+static void correct_extents (float scale_, int &dx, int &dy, int &w, int &h) {
+  if (int(scale_) == scale_) { // correct for extents non divisible by integral scale_
+    int delta = dx - int(dx/scale_)*scale_;
+    if (delta) {
+      dx -= delta; w += delta;
+    }
+    delta = -dy - int((-dy)/scale_)*scale_;
+    if (delta) {
+      dy -= delta; h += delta;
+    }
+    delta = h - int(h/scale_)*scale_;
+    if (delta) {
+      h += delta;
+    }
+    delta = w - int(w/scale_)*scale_;
+    if (delta) {
+      w += delta;
+    }
+  }
+}
 
 #if ! USE_PANGO
 
@@ -455,8 +479,8 @@ Fl_Font Fl_Xlib_Graphics_Driver::set_fonts(const char* pattern_name)
 static const char* fl_encoding_ = "iso10646-1";
 
 
-void Fl_Xlib_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize size) {
-  fl_xft_font(this,fnum,size,0);
+void Fl_Xlib_Graphics_Driver::font_unscaled(Fl_Font fnum, Fl_Fontsize size) {
+  fl_xft_font(this, fnum, size, 0);
 }
 
 static XftFont* fontopen(const char* name, /*Fl_Fontsize*/double size, bool core, int angle) {
@@ -691,17 +715,17 @@ static void utf8extents(Fl_Font_Descriptor *desc, const char *str, int n, XGlyph
 #endif
 }
 
-int Fl_Xlib_Graphics_Driver::height() {
+int Fl_Xlib_Graphics_Driver::height_unscaled() {
   if (font_descriptor()) return font_descriptor()->font->ascent + font_descriptor()->font->descent;
   else return -1;
 }
 
-int Fl_Xlib_Graphics_Driver::descent() {
+int Fl_Xlib_Graphics_Driver::descent_unscaled() {
   if (font_descriptor()) return font_descriptor()->font->descent;
   else return -1;
 }
 
-double Fl_Xlib_Graphics_Driver::width(const char* str, int n) {
+double Fl_Xlib_Graphics_Driver::width_unscaled(const char* str, int n) {
   if (!font_descriptor()) return -1.0;
   XGlyphInfo i;
   utf8extents(font_descriptor(), str, n, &i);
@@ -715,11 +739,12 @@ static double fl_xft_width(Fl_Font_Descriptor *desc, FcChar32 *str, int n) {
   return i.xOff;
 }
 
-double Fl_Xlib_Graphics_Driver::width(unsigned int c) {
+double Fl_Xlib_Graphics_Driver::width_unscaled(unsigned int c) {
+  if (!font_descriptor()) return -1.0;
   return fl_xft_width(font_descriptor(), (FcChar32 *)(&c), 1);
 }
 
-void Fl_Xlib_Graphics_Driver::text_extents(const char *c, int n, int &dx, int &dy, int &w, int &h) {
+void Fl_Xlib_Graphics_Driver::text_extents_unscaled(const char *c, int n, int &dx, int &dy, int &w, int &h) {
   if (!font_descriptor()) {
     w = h = 0;
     dx = dy = 0;
@@ -730,15 +755,12 @@ void Fl_Xlib_Graphics_Driver::text_extents(const char *c, int n, int &dx, int &d
 
   w = gi.width;
   h = gi.height;
-  dx = -gi.x;
-  dy = -gi.y;
-} // fl_text_extents
-
+  dx = -gi.x + line_delta_;
+  dy = -gi.y + line_delta_;
+  correct_extents(scale_, dx, dy, w, h);
+}
 
-void Fl_Xlib_Graphics_Driver::draw(const char *str, int n, int x, int y) {
-  if ( !this->font_descriptor() ) {
-    this->font(FL_HELVETICA, FL_NORMAL_SIZE);
-  }
+void Fl_Xlib_Graphics_Driver::draw_unscaled(const char *str, int n, int x, int y) {
 #if USE_OVERLAY
   XftDraw*& draw_ = fl_overlay ? draw_overlay : ::draw_;
   if (fl_overlay) {
@@ -756,31 +778,32 @@ void Fl_Xlib_Graphics_Driver::draw(const char *str, int n, int x, int y) {
     XftDrawChange(draw_, draw_window = fl_window);
 
   Region region = fl_clip_region();
-  if (region && XEmptyRegion(region)) return;
-  XftDrawSetClip(draw_, region);
-
-  // Use fltk's color allocator, copy the results to match what
-  // XftCollorAllocValue returns:
-  XftColor color;
-  color.pixel = fl_xpixel(Fl_Graphics_Driver::color());
-  uchar r,g,b; Fl::get_color(Fl_Graphics_Driver::color(), r,g,b);
-  color.color.red   = ((int)r)*0x101;
-  color.color.green = ((int)g)*0x101;
-  color.color.blue  = ((int)b)*0x101;
-  color.color.alpha = 0xffff;
-
-  const wchar_t *buffer = utf8reformat(str, n);
+  if (!(region && XEmptyRegion(region))) {
+    XftDrawSetClip(draw_, region);
+    
+    // Use fltk's color allocator, copy the results to match what
+    // XftCollorAllocValue returns:
+    XftColor color;
+    color.pixel = fl_xpixel(Fl_Graphics_Driver::color());
+    uchar r,g,b; Fl::get_color(Fl_Graphics_Driver::color(), r,g,b);
+    color.color.red   = ((int)r)*0x101;
+    color.color.green = ((int)g)*0x101;
+    color.color.blue  = ((int)b)*0x101;
+    color.color.alpha = 0xffff;
+    
+    const wchar_t *buffer = utf8reformat(str, n);
 #ifdef __CYGWIN__
-  XftDrawString16(draw_, &color, font_descriptor()->font, x+offset_x_, y+offset_y_, (XftChar16 *)buffer, n);
+    XftDrawString16(draw_, &color, font_descriptor()->font, x+offset_x_*scale_+line_delta_, y+offset_y_*scale_+line_delta_, (XftChar16 *)buffer, n);
 #else
-  XftDrawString32(draw_, &color, font_descriptor()->font, x+offset_x_, y+offset_y_, (XftChar32 *)buffer, n);
+    XftDrawString32(draw_, &color, font_descriptor()->font, x+offset_x_*scale_+line_delta_, y+offset_y_*scale_+line_delta_, (XftChar32 *)buffer, n);
 #endif
+  }
 }
 
-void Fl_Xlib_Graphics_Driver::draw(int angle, const char *str, int n, int x, int y) {
-  fl_xft_font(this, this->Fl_Graphics_Driver::font(), this->size(), angle);
-  this->draw(str, n, (int)x, (int)y);
-  fl_xft_font(this, this->Fl_Graphics_Driver::font(), this->size(), 0);
+void Fl_Xlib_Graphics_Driver::draw_unscaled(int angle, const char *str, int n, int x, int y) {
+  fl_xft_font(this, this->Fl_Graphics_Driver::font(), this->size_unscaled(), angle);
+  this->draw_unscaled(str, n, x, y);
+  fl_xft_font(this, this->Fl_Graphics_Driver::font(), this->size_unscaled(), 0);
 }
 
 void Fl_Xlib_Graphics_Driver::drawUCS4(const void *str, int n, int x, int y) {
@@ -814,11 +837,11 @@ void Fl_Xlib_Graphics_Driver::drawUCS4(const void *str, int n, int x, int y) {
   color.color.blue  = ((int)b)*0x101;
   color.color.alpha = 0xffff;
 
-  XftDrawString32(draw_, &color, font_descriptor()->font, x+offset_x_, y+offset_x_, (FcChar32 *)str, n);
+  XftDrawString32(draw_, &color, font_descriptor()->font, x+offset_x_*scale_+line_delta_, y+offset_y_*scale_+line_delta_, (FcChar32 *)str, n);
 }
 
 
-void Fl_Xlib_Graphics_Driver::rtl_draw(const char* c, int n, int x, int y) {
+void Fl_Xlib_Graphics_Driver::rtl_draw_unscaled(const char* c, int n, int x, int y) {
 
 #if defined(__GNUC__)
 // FIXME: warning Need to improve this XFT right to left draw function
@@ -902,7 +925,7 @@ int Fl_Xlib_Graphics_Driver::get_font_sizes(Fl_Font fnum, int*& sizep) {
 float Fl_Xlib_Graphics_Driver::scale_font_for_PostScript(Fl_Font_Descriptor *desc, int s) {
   // Xft font height is sometimes larger than the required size (see STR 2566).
   // Increase the PostScript font size by 15% without exceeding the display font height
-  int max = height();
+  int max = height_unscaled();
   float ps_size = s * 1.15;
   if (ps_size > max) ps_size = max;
   return ps_size;
@@ -972,7 +995,7 @@ static void fl_xft_font(Fl_Xlib_Graphics_Driver *driver, Fl_Font fnum, Fl_Fontsi
     return;
   }
   Fl_Font_Descriptor* f = driver->font_descriptor();
-  if (fnum == driver->Fl_Graphics_Driver::font() && size == driver->size() && f && f->angle == angle)
+  if (fnum == driver->Fl_Graphics_Driver::font() && size == driver->size_unscaled() && f && f->angle == angle)
     return;
   driver->Fl_Graphics_Driver::font(fnum, size);
   Fl_Fontdesc *font = fl_fonts + fnum;
@@ -1021,7 +1044,7 @@ static void fl_xft_font(Fl_Xlib_Graphics_Driver *driver, Fl_Font fnum, Fl_Fontsi
 //       well for the fltk "built-in" font names.
 static XFontStruct* load_xfont_for_xft2(Fl_Graphics_Driver *driver) {
   XFontStruct* xgl_font = 0;
-  int size = driver->size();
+  int size = ((Fl_Xlib_Graphics_Driver*)driver)->size_unscaled();
   int fnum = driver->font();
   const char *wt_med = "medium";
   const char *wt_bold = "bold";
@@ -1112,10 +1135,10 @@ static XFontStruct* fl_xxfont(Fl_Graphics_Driver *driver) {
   static int glsize = 0;
   static int glfont = -1;
   // Do we need to load a new font?
-  if ((!xgl_font) || (glsize != driver->size()) || (glfont != driver->font())) {
+  if ((!xgl_font) || (glsize != ((Fl_Xlib_Graphics_Driver*)driver)->size_unscaled()) || (glfont != driver->font())) {
     // create a dummy XLFD for some font of the appropriate size...
     if (xgl_font) XFreeFont(fl_display, xgl_font); // font already loaded, free it - this *might* be a Bad Idea
-    glsize = driver->size(); // record current font size
+    glsize = ((Fl_Xlib_Graphics_Driver*)driver)->size_unscaled(); // record current font size
     glfont = driver->font(); // and face
     xgl_font = load_xfont_for_xft2(driver);
   }
@@ -1126,7 +1149,7 @@ static XFontStruct* fl_xxfont(Fl_Graphics_Driver *driver) {
   }
   static XftFont* xftfont;
   if (xftfont) XftFontClose (fl_display, xftfont);
-  xftfont = fontopen(fl_fonts[driver->font()].name, driver->size(), true, 0); // else request XFT to load a suitable "core" font instead.
+  xftfont = fontopen(fl_fonts[driver->font()].name, ((Fl_Xlib_Graphics_Driver*)driver)->size_unscaled(), true, 0); // else request XFT to load a suitable "core" font instead.
   return xftfont->u.core.font;
 #  endif // XFT_MAJOR > 1
 }
@@ -1161,9 +1184,13 @@ PangoContext *Fl_Xlib_Graphics_Driver::context() {
   return pctxt_;
 }
 
-void Fl_Xlib_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize size) {
+void Fl_Xlib_Graphics_Driver::font_unscaled(Fl_Font fnum, Fl_Fontsize size) {
   if (!size) return;
-  if (this->Fl_Graphics_Driver::font() == fnum && this->size() == size) return;
+  if (size < 0) {
+    Fl_Graphics_Driver::font(0, 0);
+    return;
+  }
+  if (this->Fl_Graphics_Driver::font() == fnum && this->size_unscaled() == size) return;
   fl_xft_font(this, fnum, size, 0);
   init_built_in_fonts();
   if (pfd_) pango_font_description_free(pfd_);
@@ -1180,21 +1207,21 @@ void Fl_Xlib_Graphics_Driver::font(Fl_Font fnum, Fl_Fontsize size) {
   }
 }
 
-void Fl_Xlib_Graphics_Driver::draw(const char *str, int n, int x, int y) {
-  do_draw(0, str, n, x+offset_x_, y+offset_y_);
+void Fl_Xlib_Graphics_Driver::draw_unscaled(const char *str, int n, int x, int y) {
+  do_draw(0, str, n, x+offset_x_*scale_, y+offset_y_*scale_);
 }
 
-void Fl_Xlib_Graphics_Driver::draw(int angle, const char *str, int n, int x, int y) {
+void Fl_Xlib_Graphics_Driver::draw_unscaled(int angle, const char *str, int n, int x, int y) {
   PangoMatrix mat = PANGO_MATRIX_INIT; // 1.6
-  pango_matrix_translate(&mat, x+offset_x_, y+offset_y_); // 1.6
+  pango_matrix_translate(&mat, x+offset_x_*scale_, y+offset_y_*scale_); // 1.6
   pango_matrix_rotate(&mat, angle); // 1.6
   pango_context_set_matrix(pctxt_, &mat); // 1.6
   do_draw(0, str, n, 0, 0);
   pango_context_set_matrix(pctxt_, NULL); // 1.6
 }
 
-void Fl_Xlib_Graphics_Driver::rtl_draw(const char* str, int n, int x, int y) {
-  do_draw(1, str, n, x+offset_x_, y+offset_y_);
+void Fl_Xlib_Graphics_Driver::rtl_draw_unscaled(const char* str, int n, int x, int y) {
+  do_draw(1, str, n, x+offset_x_*scale_, y+offset_y_*scale_);
 }
 
 void Fl_Xlib_Graphics_Driver::do_draw(int from_right, const char *str, int n, int x, int y) {
@@ -1245,12 +1272,13 @@ void Fl_Xlib_Graphics_Driver::do_draw(int from_right, const char *str, int n, in
   else
     XftDrawChange(draw_, draw_window = fl_window);
   XftDrawSetClip(draw_, region);
-  pango_xft_render_layout(draw_, &color, playout_, x*PANGO_SCALE, (y-height()+descent())*PANGO_SCALE ); // 1.8
-}
+  pango_xft_render_layout(draw_, &color, playout_, (x + line_delta_)*PANGO_SCALE,
+                          (y+line_delta_-height_unscaled()+descent_unscaled())*PANGO_SCALE ); // 1.8
+  }
 
-double Fl_Xlib_Graphics_Driver::width(const char* str, int n) {
+double Fl_Xlib_Graphics_Driver::width_unscaled(const char* str, int n) {
   if (!n) return 0;
-  if (!fl_display || fl_size() == 0) return -1;
+  if (!fl_display || size_ == 0) return -1;
   if (!playout_) context();
   int width, height;
   pango_layout_set_font_description(playout_, pfd_);
@@ -1259,30 +1287,31 @@ double Fl_Xlib_Graphics_Driver::width(const char* str, int n) {
   return (double)width;
 }
 
-void Fl_Xlib_Graphics_Driver::text_extents(const char *str, int n, int &dx, int &dy, int &w, int &h) {
+void Fl_Xlib_Graphics_Driver::text_extents_unscaled(const char *str, int n, int &dx, int &dy, int &w, int &h) {
   if (!playout_) context();
   pango_layout_set_font_description(playout_, pfd_);
   pango_layout_set_text(playout_, str, n);
   PangoRectangle ink_rect, logical_rect;
   pango_layout_get_pixel_extents(playout_, &ink_rect, &logical_rect);
-  dx = ink_rect.x;
-  dy = ink_rect.y - height() + descent();
+  dx = ink_rect.x + line_delta_;
+  dy = ink_rect.y + line_delta_ - height_unscaled() + descent_unscaled();
   w = ink_rect.width;
   h = ink_rect.height;
+  correct_extents(scale_, dx, dy, w, h);
 }
 
-int Fl_Xlib_Graphics_Driver::height() {
+int Fl_Xlib_Graphics_Driver::height_unscaled() {
   if (font_descriptor())  return font_descriptor()->height_;
   else return -1;
 }
 
-double Fl_Xlib_Graphics_Driver::width(unsigned int c) {
+double Fl_Xlib_Graphics_Driver::width_unscaled(unsigned int c) {
   char buf4[4];
   int n = fl_utf8encode(c, buf4);
-  return width(buf4, n);
+  return width_unscaled(buf4, n);
 }
 
-int Fl_Xlib_Graphics_Driver::descent() {
+int Fl_Xlib_Graphics_Driver::descent_unscaled() {
   if (font_descriptor()) return font_descriptor()->descent_;
   else return -1;
 }