Support for fl_scroll() under macOS when GUI is scaled

src/Fl_cocoa.mm

@@ -3408,9 +3408,9 @@ void Fl_Cocoa_Window_Driver::make_current()
   // it gets activated when needed (e.g., draw text)
   CGContextSetShouldAntialias(gc, false);
   CGFloat hgt = [[fl_window contentView] frame].size.height;
-  CGContextTranslateCTM(gc, 0.5, hgt-0.5f);
-  CGContextScaleCTM(gc, 1.0f, -1.0f); // now 0,0 is top-left point of the window
   float s = Fl::screen_driver()->scale(0);
+  CGContextTranslateCTM(gc, 0.5f*s, hgt-0.5f*s);
+  CGContextScaleCTM(gc, 1.0f, -1.0f); // now 0,0 is top-left point of the window
   CGContextScaleCTM(gc, s, s); // apply current scaling factor
   // for subwindows, limit drawing to inside of parent window
   // half pixel offset is necessary for clipping as done by fl_cgrectmake_cocoa()

src/drivers/Cocoa/Fl_Cocoa_Window_Driver.cxx

@@ -26,6 +26,7 @@
 #include <FL/fl_draw.H>
 #include <FL/Fl.H>
 #include <FL/platform.H>
+#include <math.h>
 
 /**
  \cond DriverDev
@@ -260,7 +261,9 @@ int Fl_Cocoa_Window_Driver::scroll(int src_x, int src_y, int src_w, int src_h, i
 {
   CGImageRef img = CGImage_from_window_rect(src_x, src_y, src_w, src_h);
   if (img) {
-    ((Fl_Quartz_Graphics_Driver*)fl_graphics_driver)->draw_CGImage(img,dest_x,dest_y,src_w,src_h,0,0,src_w,src_h);
+    float s = Fl_Graphics_Driver::default_driver().scale();
+    ((Fl_Quartz_Graphics_Driver*)fl_graphics_driver)->draw_CGImage(img,
+                                      dest_x, dest_y, lround(s*src_w), lround(s*src_h), 0, 0, src_w, src_h);
     CFRelease(img);
   }
   return 0;

src/drivers/Quartz/Fl_Quartz_Graphics_Driver_image.cxx

@@ -280,32 +280,9 @@ void Fl_Quartz_Graphics_Driver::draw_CGImage(CGImageRef cgimg, int x, int y, int
   CGContextClipToRect(gc_, CGRectOffset(rect, -0.5, -0.5 ));
   // move graphics context to origin of vertically reversed image
   // The 0.5 here cancels the 0.5 offset present in Quartz graphics contexts.
-  // Thus, image and surface pixels are in phase if there's no scaling.
+  // Thus, image and surface pixels are in phase.
   CGContextTranslateCTM(gc_, rect.origin.x - srcx - 0.5, rect.origin.y - srcy + sh - 0.5);
   CGContextScaleCTM(gc_, 1, -1);
-  CGAffineTransform at = CGContextGetCTM(gc_);
-  if (at.a == at.d && at.b == 0 && at.c == 0) { // proportional scaling, no rotation
-    // We handle x2 and /2 scalings that occur when drawing to
-    // a double-resolution bitmap, and when drawing a double-resolution bitmap to display.
-    bool doit = false;
-    // phase image with display pixels
-    CGFloat deltax = 0, deltay = 0;
-    if (at.a == 2) { // make .tx and .ty have even values
-      deltax = (at.tx/2 - round(at.tx/2));
-      deltay = (at.ty/2 - round(at.ty/2));
-      doit = true;
-    } else if (at.a == 0.5) {
-      doit = true;
-      if (high_resolution()) { // make .tx and .ty have int or half-int values
-        deltax = -(at.tx*2 - round(at.tx*2));
-        deltay = (at.ty*2 - round(at.ty*2));
-      } else { // make .tx and .ty have integral values
-        deltax = (at.tx - round(at.tx))*2;
-        deltay = (at.ty - round(at.ty))*2;
-      }
-    }
-    if (doit) CGContextTranslateCTM(gc_, -deltax, -deltay);
-  }
   CGContextDrawImage(gc_, CGRectMake(0, 0, sw, sh), cgimg);
   CGContextRestoreGState(gc_);
 }

src/drivers/Quartz/Fl_Quartz_Graphics_Driver_rect.cxx

@@ -75,7 +75,7 @@ void Fl_Quartz_Graphics_Driver::xyline(int x, int y, int x1) {
   CGContextMoveToPoint(gc_, x, y);
   CGContextAddLineToPoint(gc_, x1, y);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     /* On retina displays, all xyline() and yxline() functions produce lines that are half-unit
      (or one pixel) too short at both ends. This is corrected by filling at both ends rectangles
      of size one unit by line-width.
@@ -92,7 +92,7 @@ void Fl_Quartz_Graphics_Driver::xyline(int x, int y, int x1, int y2) {
   CGContextAddLineToPoint(gc_, x1, y);
   CGContextAddLineToPoint(gc_, x1, y2);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     CGContextFillRect(gc_, CGRectMake(x-0.5, y  - quartz_line_width_/2, 1 , quartz_line_width_));
     CGContextFillRect(gc_, CGRectMake(x1  -  quartz_line_width_/2, y2-0.5, quartz_line_width_, 1));
   }
@@ -106,7 +106,7 @@ void Fl_Quartz_Graphics_Driver::xyline(int x, int y, int x1, int y2, int x3) {
   CGContextAddLineToPoint(gc_, x1, y2);
   CGContextAddLineToPoint(gc_, x3, y2);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     CGContextFillRect(gc_, CGRectMake(x-0.5, y  - quartz_line_width_/2, 1 , quartz_line_width_));
     CGContextFillRect(gc_, CGRectMake(x3-0.5, y2  - quartz_line_width_/2, 1 , quartz_line_width_));
   }
@@ -118,7 +118,7 @@ void Fl_Quartz_Graphics_Driver::yxline(int x, int y, int y1) {
   CGContextMoveToPoint(gc_, x, y);
   CGContextAddLineToPoint(gc_, x, y1);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     CGContextFillRect(gc_, CGRectMake(x  -  quartz_line_width_/2, y-0.5, quartz_line_width_, 1));
     CGContextFillRect(gc_, CGRectMake(x  -  quartz_line_width_/2, y1-0.5, quartz_line_width_, 1));
   }
@@ -131,7 +131,7 @@ void Fl_Quartz_Graphics_Driver::yxline(int x, int y, int y1, int x2) {
   CGContextAddLineToPoint(gc_, x, y1);
   CGContextAddLineToPoint(gc_, x2, y1);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     CGContextFillRect(gc_, CGRectMake(x  -  quartz_line_width_/2, y-0.5, quartz_line_width_, 1));
     CGContextFillRect(gc_, CGRectMake(x2-0.5, y1  - quartz_line_width_/2, 1 , quartz_line_width_));
   }
@@ -145,7 +145,7 @@ void Fl_Quartz_Graphics_Driver::yxline(int x, int y, int y1, int x2, int y3) {
   CGContextAddLineToPoint(gc_, x2, y1);
   CGContextAddLineToPoint(gc_, x2, y3);
   CGContextStrokePath(gc_);
-  if (high_resolution()) {
+  if (high_resolution() || scale()>=2) {
     CGContextFillRect(gc_, CGRectMake(x  -  quartz_line_width_/2, y-0.5, quartz_line_width_, 1));
     CGContextFillRect(gc_, CGRectMake(x2  -  quartz_line_width_/2, y3-0.5, quartz_line_width_, 1));
   }