From 2715deac1d9245d146ea9c0c42139167dc92eb37 Mon Sep 17 00:00:00 2001
From: Shahzaib Ibrahim <shahzaibibrahim96@gmail.com>
Date: Wed, 10 Dec 2025 14:37:58 +0100
Subject: [PATCH] Deprecating Display#getDPI

Having the scale factor being based on the screen DPI leads to
unexpected result e.g. Image too big/small. Having a screen dpi
independent factor leads to consistent results.
---
 .../cocoa/org/eclipse/swt/graphics/Device.java  | 16 ++++++++++++++--
 .../gtk/org/eclipse/swt/graphics/Device.java    | 17 ++++++++++++++---
 .../win32/org/eclipse/swt/graphics/Device.java  | 11 +++++++++++
 3 files changed, 39 insertions(+), 5 deletions(-)

diff --git a/bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Device.java b/bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Device.java
index ef30e780765..36a6e040824 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Device.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/graphics/Device.java	
@@ -391,7 +391,18 @@ public int getDepth () {
  * @exception SWTException <ul>
  *    <li>ERROR_DEVICE_DISPOSED - if the receiver has been disposed</li>
  * </ul>
+ *
+ * @deprecated <p>This method returns a single global DPI value
+ * that does not reflect per-monitor DPI settings on modern operating systems.
+ * In environments with different scaling factors across monitors, it may provide
+ * a misleading or meaningless result, as it does not correspond to the actual DPI
+ * of any specific monitor.</p>
+ *
+ * <p>Note: While deprecated for general {@code Device} instances like {@code Display},
+ * this method may still be validly used when called on a {@code Printer} instance,
+ * where a single global DPI value is meaningful and expected.</p>
  */
+@Deprecated
 public Point getDPI () {
 	checkDevice ();
 	return getScreenDPI();
@@ -611,8 +622,9 @@ protected void init () {
 	/* Initialize the system font slot */
 	boolean smallFonts = System.getProperty("org.eclipse.swt.internal.carbon.smallFonts") != null;
 	double systemFontSize = smallFonts ? NSFont.smallSystemFontSize() : NSFont.systemFontSize();
-	Point dpi = this.dpi = getDPI(), screenDPI = getScreenDPI();
-	NSFont font = NSFont.systemFontOfSize(systemFontSize * dpi.y / screenDPI.y);
+	final int DOTS_PER_INCH = 72;
+	Point dpi = this.dpi = getDPI();
+	NSFont font = NSFont.systemFontOfSize(systemFontSize * dpi.y / DOTS_PER_INCH);
 	font.retain();
 	systemFont = Font.cocoa_new(this, font);
 }
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java
index d329fb6670f..48c9d9bab5f 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/graphics/Device.java	
@@ -455,7 +455,18 @@ public int getDepth () {
  * @exception SWTException <ul>
  *    <li>ERROR_DEVICE_DISPOSED - if the receiver has been disposed</li>
  * </ul>
+ *
+ * @deprecated <p>This method returns a single global DPI value
+ * that does not reflect per-monitor DPI settings on modern operating systems.
+ * In environments with different scaling factors across monitors, it may provide
+ * a misleading or meaningless result, as it does not correspond to the actual DPI
+ * of any specific monitor.</p>
+ *
+ * <p>Note: While deprecated for general {@code Device} instances like {@code Display},
+ * this method may still be validly used when called on a {@code Printer} instance,
+ * where a single global DPI value is meaningful and expected.</p>
  */
+@Deprecated
 public Point getDPI () {
 	checkDevice ();
 	return getScreenDPI();
@@ -641,6 +652,7 @@ public boolean getWarnings () {
  * @see #create
  */
 protected void init () {
+	final int DOTS_PER_INCH = 96;
 	if (debug) {
 		if (xDisplay != 0) {
 			/* Create the warning and error callbacks */
@@ -723,10 +735,9 @@ protected void init () {
 		}
 	}
 	defaultFont = OS.pango_font_description_copy (defaultFont);
-	Point dpi = getDPI(), screenDPI = getScreenDPI();
-	if (dpi.y != screenDPI.y) {
+	if (this.dpi.y != DOTS_PER_INCH) {
 		int size = OS.pango_font_description_get_size(defaultFont);
-		OS.pango_font_description_set_size(defaultFont, size * dpi.y / screenDPI.y);
+		OS.pango_font_description_set_size(defaultFont, size * this.dpi.y / DOTS_PER_INCH);
 	}
 	systemFont = Font.gtk_new (this, defaultFont);
 
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Device.java b/bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Device.java
index 04c7c51b1c4..1a3783448d3 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Device.java	
+++ b/bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/graphics/Device.java	
@@ -519,7 +519,18 @@ public int getDepth () {
  * @exception SWTException <ul>
  *    <li>ERROR_DEVICE_DISPOSED - if the receiver has been disposed</li>
  * </ul>
+ *
+ * @deprecated <p>This method returns a single global DPI value
+ * that does not reflect per-monitor DPI settings on modern operating systems.
+ * In environments with different scaling factors across monitors, it may provide
+ * a misleading or meaningless result, as it does not correspond to the actual DPI
+ * of any specific monitor.</p>
+ *
+ * <p>Note: While deprecated for general {@code Device} instances like {@code Display},
+ * this method may still be validly used when called on a {@code Printer} instance,
+ * where a single global DPI value is meaningful and expected.</p>
  */
+@Deprecated
 public Point getDPI () {
 	checkDevice ();
 	long hDC = internal_new_GC (null);