commit bef46b5cb82464713a117b9bdb920735d1b7de37
Author:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
AuthorDate: Wed Feb 24 14:52:36 2021 +0100
Commit:     ManoloFLTK <41016272+ManoloFLTK@users.noreply.github.com>
CommitDate: Wed Feb 24 14:52:47 2021 +0100

    Improve precision of GUI scaling for Windows platform.

 FL/Fl_Graphics_Driver.H                          |   4 +
 src/Fl_Graphics_Driver.cxx                       |  16 +++
 src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx   |   2 +-
 src/drivers/GDI/Fl_GDI_Graphics_Driver.H         |  18 ++-
 src/drivers/GDI/Fl_GDI_Graphics_Driver.cxx       |  21 ++--
 src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx |  22 ++--
 src/drivers/GDI/Fl_GDI_Graphics_Driver_rect.cxx  | 134 +++++++++++++++--------
 src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx   |  10 +-
 8 files changed, 152 insertions(+), 75 deletions(-)

diff --git FL/Fl_Graphics_Driver.H FL/Fl_Graphics_Driver.H
index 2c33212..8a7a93b 100644
--- FL/Fl_Graphics_Driver.H
+++ FL/Fl_Graphics_Driver.H
@@ -237,6 +237,7 @@ protected:
 
   Fl_Graphics_Driver();
   virtual void cache_size(Fl_Image *img, int &width, int &height);
+  void cache_size_finalize(Fl_Image *img, int &width, int &height);
   static unsigned need_pixmap_bg_color;
 public:
   virtual ~Fl_Graphics_Driver() {} ///< Destructor
@@ -444,6 +445,7 @@ protected:
   virtual void circle(double x, double y, double r);
   virtual void ellipse_unscaled(double xt, double yt, double rx, double ry);
   virtual void font(Fl_Font face, Fl_Fontsize size);
+  virtual Fl_Font font();
   virtual void font_unscaled(Fl_Font face, Fl_Fontsize size);
   virtual double width(const char *str, int n);
   virtual double width(unsigned int c);
@@ -461,8 +463,10 @@ protected:
   virtual void draw_unscaled(const char *str, int n, int x, int y);
   virtual void draw(int angle, const char *str, int n, int x, int y);
   virtual void draw_unscaled(int angle, const char *str, int n, int x, int y);
+  virtual void draw(const char *str, int nChars, float x, float y);
   virtual void rtl_draw(const char* str, int n, int x, int y);
   virtual void rtl_draw_unscaled(const char* str, int n, int x, int y);
+  virtual void arc(double x, double y, double r, double start, double end);
   virtual void arc(int x, int y, int w, int h, double a1, double a2);
   virtual void arc_unscaled(float x, float y, float w, float h, double a1, double a2);
   virtual void pie(int x, int y, int w, int h, double a1, double a2);
diff --git src/Fl_Graphics_Driver.cxx src/Fl_Graphics_Driver.cxx
index ec3cc8d..2f687e1 100644
--- src/Fl_Graphics_Driver.cxx
+++ src/Fl_Graphics_Driver.cxx
@@ -211,6 +211,10 @@ void Fl_Graphics_Driver::cache_size(Fl_Image *img, int &width, int &height)
   fs = height * s;
   height = (fs - int(fs) < 0.001 ? int(fs) :
            int((height+1) * s));
+  cache_size_finalize(img, width, height);
+}
+
+void Fl_Graphics_Driver::cache_size_finalize(Fl_Image *img, int &width, int &height) {
   if (img) img->cache_size_(width, height);
 }
 
@@ -754,6 +758,10 @@ void Fl_Scalable_Graphics_Driver::font(Fl_Font face, Fl_Fontsize size) {
   font_unscaled(face, Fl_Fontsize(size * scale()));
 }
 
+Fl_Font Fl_Scalable_Graphics_Driver::font() {
+  return Fl_Graphics_Driver::font();
+}
+
 double Fl_Scalable_Graphics_Driver::width(const char *str, int n) {
   return width_unscaled(str, n)/scale();
 }
@@ -790,6 +798,10 @@ void Fl_Scalable_Graphics_Driver::draw(const char *str, int n, int x, int y) {
   unscale_clip(r2);
 }
 
+void Fl_Scalable_Graphics_Driver::draw(const char *str, int n, float x, float y) {
+  Fl_Graphics_Driver::draw(str, n, x, y);
+}
+
 void Fl_Scalable_Graphics_Driver::draw(int angle, const char *str, int n, int x, int y) {
   if (!size_ || !font_descriptor()) font(FL_HELVETICA, FL_NORMAL_SIZE);
   Fl_Region r2 = scale_clip(scale());
@@ -805,6 +817,10 @@ void Fl_Scalable_Graphics_Driver::arc(int x,int y,int w,int h,double a1,double a
   arc_unscaled(x * scale(), y * scale(), w * scale(), h * scale(), a1, a2);
 }
 
+void Fl_Scalable_Graphics_Driver::arc(double x, double y, double r, double start, double end) {
+  Fl_Graphics_Driver::arc(x, y, r, start, end);
+}
+
 void Fl_Scalable_Graphics_Driver::pie(int x,int y,int w,int h,double a1,double a2) {
   pie_unscaled(x * scale(), y * scale(), w * scale(), h * scale(), a1, a2);
 }
diff --git src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx
index 7117c6c..b73c72e 100644
--- src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx
+++ src/drivers/GDI/Fl_GDI_Copy_Surface_Driver.cxx
@@ -75,7 +75,7 @@ Fl_GDI_Copy_Surface_Driver::~Fl_GDI_Copy_Surface_Driver() {
       SetClipboardData (CF_ENHMETAFILE, hmf);
       // then put a BITMAP version of the graphics in the clipboard
       float scaling = driver()->scale();
-      int W = int(width * scaling), H = int(height * scaling);
+      int W = Fl_GDI_Graphics_Driver::floor(width, scaling), H = Fl_GDI_Graphics_Driver::floor(height, scaling);
       RECT rect = {0, 0, W, H};
       Fl_Image_Surface *surf = new Fl_Image_Surface(W, H);
       Fl_Surface_Device::push_current(surf);
diff --git src/drivers/GDI/Fl_GDI_Graphics_Driver.H src/drivers/GDI/Fl_GDI_Graphics_Driver.H
index e2a29da..d322bc8 100644
--- src/drivers/GDI/Fl_GDI_Graphics_Driver.H
+++ src/drivers/GDI/Fl_GDI_Graphics_Driver.H
@@ -58,6 +58,11 @@ public:
   char can_do_alpha_blending();
   virtual void gc(void *ctxt) { gc_ = (HDC)ctxt; global_gc(); }
   virtual void *gc() {return gc_;}
+  // This function aims to compute accurately int(x * s) in
+  // presence of rounding errors existing with floating point numbers
+  // and that sometimes differ between 32 and 64 bits.
+  static inline int floor(int x, float s) { return int(x * s + 0.001f); }
+  inline int floor(int x) { return Fl_GDI_Graphics_Driver::floor(x, scale()); }
 
   // --- bitmap stuff
   Fl_Bitmask create_bitmask(int w, int h, const uchar *array);
@@ -96,14 +101,18 @@ public:
 protected:
   void transformed_vertex0(float x, float y);
   void fixloop();
-  virtual void point_unscaled(float x, float y);
+  virtual void point(int x, int y);
   virtual void rect(int x, int y, int w, int h);
   void focus_rect(int x, int y, int w, int h);
-  void rectf_unscaled(float x, float y, float w, float h);
+  virtual void rectf(int x, int y, int w, int h);
   virtual void line_unscaled(float x, float y, float x1, float y1);
   virtual void line_unscaled(float x, float y, float x1, float y1, float x2, float y2);
-  virtual void xyline_unscaled(float x, float y, float x1);
-  virtual void yxline_unscaled(float x, float y, float y1);
+  virtual void xyline(int x, int y, int x1);
+  virtual void xyline(int x, int y, int x1, int y2);
+  virtual void xyline(int x, int y, int x1, int y2, int x3);
+  virtual void yxline(int x, int y, int y1);
+  virtual void yxline(int x, int y, int y1, int x2);
+  virtual void yxline(int x, int y, int y1, int x2, int y3);
   virtual void loop_unscaled(float x0, float y0, float x1, float y1, float x2, float y2);
   virtual void loop_unscaled(float x0, float y0, float x1, float y1, float x2, float y2, float x3, float y3);
   virtual void polygon_unscaled(float x0, float y0, float x1, float y1, float x2, float y2);
@@ -144,6 +153,7 @@ protected:
   virtual void font_name(int num, const char *name);
   void global_gc();
   virtual void overlay_rect(int x, int y, int w , int h);
+  virtual void cache_size(Fl_Image *img, int &width, int &height);
 };
 
 
diff --git src/drivers/GDI/Fl_GDI_Graphics_Driver.cxx src/drivers/GDI/Fl_GDI_Graphics_Driver.cxx
index dd9ed5d..09dd6fa 100644
--- src/drivers/GDI/Fl_GDI_Graphics_Driver.cxx
+++ src/drivers/GDI/Fl_GDI_Graphics_Driver.cxx
@@ -260,15 +260,14 @@ HRGN Fl_GDI_Graphics_Driver::scale_region(HRGN r, float f, Fl_GDI_Graphics_Drive
       pt.y = int(pt.y * (f - 1));
     }
     RECT *rects = (RECT*)&(pdata->Buffer);
-    int delta = (f > 1.75 ? 1 : 0) - int(f/2);
     for (DWORD i = 0; i < pdata->rdh.nCount; i++) {
-      int x = int(rects[i].left * f) + pt.x;
-      int y = int(rects[i].top * f) + pt.y;
+      int x = Fl_GDI_Graphics_Driver::floor(rects[i].left, f) + pt.x;
+      int y = Fl_GDI_Graphics_Driver::floor(rects[i].top, f) + pt.y;
       RECT R2;
-      R2.left = x + delta;
-      R2.top  = y + delta;
-      R2.right = int(rects[i].right * f) + pt.x - x + R2.left;
-      R2.bottom = int(rects[i].bottom * f) + pt.y - y + R2.top;
+      R2.left = x;
+      R2.top  = y;
+      R2.right = Fl_GDI_Graphics_Driver::floor(rects[i].right, f) + pt.x - x + R2.left;
+      R2.bottom = Fl_GDI_Graphics_Driver::floor(rects[i].bottom, f) + pt.y - y + R2.top;
       rects[i] = R2;
     }
     r = ExtCreateRegion(NULL, size, pdata);
@@ -287,3 +286,11 @@ Fl_Region Fl_GDI_Graphics_Driver::scale_clip(float f) {
 void Fl_GDI_Graphics_Driver::set_current_() {
   restore_clip();
 }
+
+void Fl_GDI_Graphics_Driver::cache_size(Fl_Image *img, int &width, int &height)
+{
+  float s = scale();
+  width  = (s == int(s) ? width * int(s) : floor(width+1));
+  height = (s == int(s) ? height * int(s) : floor(height+1));
+  cache_size_finalize(img, width, height);
+}
diff --git src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
index 0135eb6..29fd653 100644
--- src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
+++ src/drivers/GDI/Fl_GDI_Graphics_Driver_image.cxx
@@ -398,10 +398,10 @@ void Fl_GDI_Graphics_Driver::delete_bitmask(Fl_Bitmask bm) {
 }
 
 void Fl_GDI_Graphics_Driver::draw_fixed(Fl_Bitmap *bm, int X, int Y, int W, int H, int cx, int cy) {
-  X = int(X * scale());
-  Y = int(Y * scale());
+  X = this->floor(X);
+  Y = this->floor(Y);
   cache_size(bm, W, H);
-  cx = int(cx * scale()); cy = int(cy * scale());
+  cx = this->floor(cx); cy = this->floor(cy);
 
   HDC tempdc = CreateCompatibleDC(gc_);
   int save = SaveDC(tempdc);
@@ -499,10 +499,10 @@ void Fl_GDI_Graphics_Driver::cache(Fl_RGB_Image *img)
 
 
 void Fl_GDI_Graphics_Driver::draw_fixed(Fl_RGB_Image *img, int X, int Y, int W, int H, int cx, int cy) {
-  X = int(X * scale());
-  Y = int(Y * scale());
+  X = this->floor(X);
+  Y = this->floor(Y);
   cache_size(img, W, H);
-  cx = int(cx * scale()); cy = int(cy * scale());
+  cx = this->floor(cx); cy = this->floor(cy);
   if (W + cx > img->data_w()) W = img->data_w() - cx;
   if (H + cy > img->data_h()) H = img->data_h() - cy;
   if (!*Fl_Graphics_Driver::id(img)) {
@@ -547,10 +547,10 @@ void Fl_GDI_Graphics_Driver::draw_rgb(Fl_RGB_Image *rgb, int XP, int YP, int WP,
   int save = SaveDC(new_gc);
   SelectObject(new_gc, (HBITMAP)*Fl_Graphics_Driver::id(rgb));
   if ( (rgb->d() % 2) == 0 ) {
-    alpha_blend_(int(XP*scale()), int(YP*scale()), W, H, new_gc, 0, 0, rgb->data_w(), rgb->data_h());
+    alpha_blend_(this->floor(XP), this->floor(YP), W, H, new_gc, 0, 0, rgb->data_w(), rgb->data_h());
   } else {
     SetStretchBltMode(gc_, HALFTONE);
-    StretchBlt(gc_, int(XP*scale()), int(YP*scale()), W, H, new_gc, 0, 0, rgb->data_w(), rgb->data_h(), SRCCOPY);
+    StretchBlt(gc_, this->floor(XP), this->floor(YP), W, H, new_gc, 0, 0, rgb->data_w(), rgb->data_h(), SRCCOPY);
   }
   RestoreDC(new_gc, save);
   DeleteDC(new_gc);
@@ -631,10 +631,10 @@ void Fl_GDI_Graphics_Driver::cache(Fl_Bitmap *bm) {
 }
 
 void Fl_GDI_Graphics_Driver::draw_fixed(Fl_Pixmap *pxm, int X, int Y, int W, int H, int cx, int cy) {
-  X = int(X * scale());
-  Y = int(Y * scale());
+  X = this->floor(X);
+  Y = this->floor(Y);
   cache_size(pxm, W, H);
-  cx = int(cx * scale()); cy = int(cy * scale());
+  cx = this->floor(cx); cy = this->floor(cy);
   Fl_Region r2 = scale_clip(scale());
   if (*Fl_Graphics_Driver::mask(pxm)) {
     HDC new_gc = CreateCompatibleDC(gc_);
diff --git src/drivers/GDI/Fl_GDI_Graphics_Driver_rect.cxx src/drivers/GDI/Fl_GDI_Graphics_Driver_rect.cxx
index 8e45c6e..4a8daeb 100644
--- src/drivers/GDI/Fl_GDI_Graphics_Driver_rect.cxx
+++ src/drivers/GDI/Fl_GDI_Graphics_Driver_rect.cxx
@@ -31,47 +31,51 @@
 
 // --- line and polygon drawing with integer coordinates
 
-void Fl_GDI_Graphics_Driver::point_unscaled(float fx, float fy) {
-  int width = (scale() >= 1 ? int(scale()) : 1);
-  RECT rect;
-  rect.left = int(fx); rect.top = int(fy);
-  rect.right = int(fx) + width; rect.bottom = int(fy) + width;
-  FillRect(gc_, &rect, fl_brush());
+void Fl_GDI_Graphics_Driver::point(int x, int y) {
+  rectf(x, y, 1, 1);
 }
 
 void Fl_GDI_Graphics_Driver::overlay_rect(int x, int y, int w , int h) {
   // make pen have a one-pixel width
   line_style_unscaled( (color()==FL_WHITE?FL_SOLID:FL_DOT), 1, NULL);
-  loop(x, y, x+w-1, y, x+w-1, y+h-1, x, y+h-1);
+  int right = this->floor(x+w-1), bottom = this->floor(y+h-1);
+  x = this->floor(x); y = this->floor(y);
+  MoveToEx(gc_, x, y, 0L);
+  LineTo(gc_, right, y);
+  LineTo(gc_, right, bottom);
+  LineTo(gc_, x, bottom);
+  LineTo(gc_, x, y);
 }
 
 void Fl_GDI_Graphics_Driver::rect(int x, int y, int w, int h)
 {
   if (w > 0 && h > 0) {
-    float s = scale();
-    xyline_unscaled(x*s, y*s, (x+w-1)*s);
-    yxline_unscaled(x*s, y*s, (y+h-1)*s);
-    yxline_unscaled((x+w-1)*s, y*s, (y+h-1)*s);
-    xyline_unscaled(x*s, (y+h-1)*s, (x+w-1)*s);
+    xyline(x, y, (x+w-1));
+    yxline(x, y, (y+h-1));
+    yxline((x+w-1), y, (y+h-1));
+    xyline(x, (y+h-1), (x+w-1));
   }
 }
 
 void Fl_GDI_Graphics_Driver::focus_rect(int x, int y, int w, int h) {
   // Windows 95/98/ME do not implement the dotted line style, so draw
   // every other pixel around the focus area...
-  w--; h--;
+  w = floor(x+w-1) - floor(x) + 1;
+  h = floor(y+h-1) - floor(y) + 1;
+  x = floor(x); y = floor(y);
   int i=1, xx, yy;
-  for (xx = 0; xx < w; xx++, i++) if (i & 1) point(x + xx, y);
-  for (yy = 0; yy < h; yy++, i++) if (i & 1) point(x + w, y + yy);
-  for (xx = w; xx > 0; xx--, i++) if (i & 1) point(x + xx, y + h);
-  for (yy = h; yy > 0; yy--, i++) if (i & 1) point(x, y + yy);
+  COLORREF c = fl_RGB();
+  for (xx = 0; xx < w; xx++, i++) if (i & 1) SetPixel(gc_, x+xx, y, c);
+  for (yy = 0; yy < h; yy++, i++) if (i & 1) SetPixel(gc_, x+w, y+yy, c);
+  for (xx = w; xx > 0; xx--, i++) if (i & 1) SetPixel(gc_, x+xx, y+h, c);
+  for (yy = h; yy > 0; yy--, i++) if (i & 1) SetPixel(gc_, x, y+yy, c);
 }
 
-void Fl_GDI_Graphics_Driver::rectf_unscaled(float x, float y, float w, float h) {
+void Fl_GDI_Graphics_Driver::rectf(int x, int y, int w, int h) {
   if (w<=0 || h<=0) return;
   RECT rect;
-  rect.left = int(x); rect.top = int(y);
-  rect.right = int(x + w); rect.bottom = int(y + h);
+  rect.left = this->floor(x); rect.top = this->floor(y);
+  rect.right = this->floor(x + w); rect.bottom = this->floor(y + h);
   FillRect(gc_, &rect, fl_brush());
 }
 
@@ -88,38 +92,74 @@ void Fl_GDI_Graphics_Driver::line_unscaled(float x, float y, float x1, float y1,
   SetPixel(gc_, int(x2), int(y2), fl_RGB());
 }
 
-void Fl_GDI_Graphics_Driver::xyline_unscaled(float x, float y, float x1) {
-  int line_delta_ =  (scale() > 1.75 ? 1 : 0);
-  int tw = line_width_ ? line_width_ : 1; // true line width
-  if (x > x1) { float exch = x; x = x1; x1 = exch; }
-  int ix = int(x) + line_delta_; if (scale() >= 2.f) ix -= int(scale()/2);
-  int iy = int(y) + line_delta_;
-  if (scale() > 1.9 && line_width_/scale() >= 2) iy--;
-  int ix1 = int( int(x1/scale()+1.5f) * scale() ) - 1; // extend line to pixel before line beginning at x1/scale_ + 1
-  ix1 += line_delta_; if (scale() >= 2) ix1 -= 1;; if (scale() >= 4) ix1 -= 1;
-  MoveToEx(gc_, ix, iy, 0L); LineTo(gc_, ix1+1, iy);
-  // try and make sure no unfilled area lies between xyline(x,y,x1) and xyline(x,y+1,x1)
-  if (int(scale()) != scale() && y+line_delta_ + scale() >= iy + tw+1 - 0.001 ) {
-    MoveToEx(gc_, ix, iy+1, 0L); LineTo(gc_, ix1+1, iy+1);
+static HPEN change_pen_width(int width, HDC gc) { // set the width of the pen, return previous pen
+  LOGBRUSH penbrush = {BS_SOLID, fl_RGB(), 0};
+  HPEN newpen = ExtCreatePen(PS_GEOMETRIC | PS_ENDCAP_FLAT | PS_JOIN_ROUND, width, &penbrush, 0, 0);
+  return (HPEN)SelectObject(gc, newpen);
+}
+
+void Fl_GDI_Graphics_Driver::xyline(int x, int y, int x1) {
+  if (y < 0) return;
+  float s = scale();
+  int xx = (x < x1 ? x : x1);
+  int xx1 = (x < x1 ? x1 : x);
+  if (s != int(s) && line_width_ <= int(s)) {
+    int lwidth = this->floor((y+1)) - this->floor(y);
+    bool need_pen = (lwidth != int(s));
+    HPEN oldpen = (need_pen ? change_pen_width(lwidth, gc_) : NULL);
+    MoveToEx(gc_, this->floor(xx), this->floor(y) + int(lwidth/2.f) , 0L);
+    LineTo(gc_, this->floor((xx1+1)), this->floor(y) + int(lwidth/2.f));
+    if (need_pen) {
+      DeleteObject(SelectObject(gc_, oldpen));
+    }
+  } else {
+    y = int((y + 0.5f) * s);
+    MoveToEx(gc_, this->floor(xx), y, 0L);
+    LineTo(gc_, this->floor(xx1) + int(s) , y);
   }
 }
 
-void Fl_GDI_Graphics_Driver::yxline_unscaled(float x, float y, float y1) {
-  if (y1 < y) { float exch = y; y = y1; y1 = exch;}
-  int line_delta_ =  (scale() > 1.75 ? 1 : 0);
-  int tw = line_width_ ? line_width_ : 1; // true line width
-
-  int ix = int(x) + line_delta_;
-  if (scale() > 1.9 && line_width_/scale() >= 2) ix--;
-  int iy = int(y) + line_delta_; if (scale() >= 2) iy -= int(scale()/2);
-  int iy1 = int( int(y1/scale()+1.5) * scale() ) - 1;
-  iy1 += line_delta_; if (scale() >= 2) iy1 -= 1;; if (scale() >= 4) iy1 -= 1; // extend line to pixel before line beginning at y1/scale_ + 1
-  MoveToEx(gc_, ix, iy, 0L); LineTo(gc_, ix, iy1+1);
-  // try and make sure no unfilled area lies between yxline(x,y,y1) and yxline(x+1,y,y1)
-  if (int(scale()) != scale() && x+line_delta_+scale() >= ix + tw+1 -0.001) {
-    MoveToEx(gc_, ix+1, iy, 0L); LineTo(gc_, ix+1, iy1+1);
+void Fl_GDI_Graphics_Driver::xyline(int x, int y, int x1, int y2) {
+  xyline(x, y, x1);
+  yxline(x1, y, y2);
+}
+
+void Fl_GDI_Graphics_Driver::xyline(int x, int y, int x1, int y2, int x3) {
+  xyline(x, y, x1);
+  yxline(x1, y, y2);
+  xyline(x1, y2, x3);
+}
+
+void Fl_GDI_Graphics_Driver::yxline(int x, int y, int y1) {
+  if (x < 0) return;
+  double s = scale();
+  int yy = (y < y1 ? y : y1);
+  int yy1 = (y < y1 ? y1 : y);
+  if (s != int(s) && line_width_ <= int(s)) {
+    int lwidth = (this->floor((x+1)) - this->floor(x));
+    bool need_pen = (lwidth != int(s));
+    HPEN oldpen = (need_pen ? change_pen_width(lwidth, gc_) : NULL);
+    MoveToEx(gc_, this->floor(x) + int(lwidth/2.f), this->floor(yy), 0L);
+    LineTo(gc_, this->floor(x) + int(lwidth/2.f), this->floor((yy1+1)) );
+    if (need_pen) {
+      DeleteObject(SelectObject(gc_, oldpen));
+    }
+  } else {
+    x = int((x + 0.5f) * s);
+    MoveToEx(gc_, x, this->floor(yy), 0L);
+    LineTo(gc_, x, this->floor(yy1) + int(s));
   }
+}
+
+void Fl_GDI_Graphics_Driver::yxline(int x, int y, int y1, int x2) {
+  yxline(x, y, y1);
+  xyline(x, y1, x2);
+}
 
+void Fl_GDI_Graphics_Driver::yxline(int x, int y, int y1, int x2, int y3) {
+  yxline(x, y, y1);
+  xyline(x, y1, x2);
+  yxline(x2, y1, y3);
 }
 
 void Fl_GDI_Graphics_Driver::loop_unscaled(float x, float y, float x1, float y1, float x2, float y2) {
diff --git src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
index 7c57d08..eb437b9 100644
--- src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
+++ src/drivers/WinAPI/Fl_WinAPI_Screen_Driver.cxx
@@ -20,7 +20,7 @@
 #include "../GDI/Fl_Font.H"
 #include <FL/Fl.H>
 #include <FL/platform.H>
-#include <FL/Fl_Graphics_Driver.H>
+#include "../GDI/Fl_GDI_Graphics_Driver.H"
 #include <FL/Fl_RGB_Image.H>
 #include <FL/fl_ask.H>
 #include <stdio.h>
@@ -499,14 +499,14 @@ Fl_WinAPI_Screen_Driver::read_win_rectangle(
 {
   float s = Fl_Surface_Device::surface()->driver()->scale();
   int ws, hs;
-  if (int(s) == s) { ws = int(w * s); hs = int(h * s);}
+  if (int(s) == s) { ws = w * int(s); hs = h * int(s);}
   else {
-    ws = int((w+1) * s); // approximates what Fl_Graphics_Driver::cache_size() does
-    hs = int((h+1) * s);
+    ws = Fl_GDI_Graphics_Driver::floor(w+1, s); // approximates what Fl_Graphics_Driver::cache_size() does
+    hs = Fl_GDI_Graphics_Driver::floor(h+1, s);
     if (ws < 1) ws = 1;
     if (hs < 1) hs = 1;
   }
-  return read_win_rectangle_unscaled(int(X*s), int(Y*s), ws, hs, win);
+  return read_win_rectangle_unscaled(Fl_GDI_Graphics_Driver::floor(X, s), Fl_GDI_Graphics_Driver::floor(Y, s), ws, hs, win);
 }
 
 Fl_RGB_Image *Fl_WinAPI_Screen_Driver::read_win_rectangle_unscaled(int X, int Y, int w, int h, Fl_Window *win)