[Win32] Normalise \r and \r\n to \n in GDI+ text rendering

[HeikoKlare]

Summary

GDI+ Graphics_DrawString only treats \n as a line delimiter; bare \r is silently ignored rather than treated as a line break. The GDI DrawText path (non-advanced mode) and the old DrawDriverString path both accept \r and \r\n as line delimiters, so callers that pass Windows-style (CRLF) or old Mac-style (CR-only) line endings with DRAW_DELIMITER set get different results depending on whether advanced mode is active.

• Fix: in drawTextGDIP(), when DRAW_DELIMITER is active, normalise \r\n → \n first (to avoid double line breaks), then convert any remaining lone \r → \n before passing the string to Graphics_DrawString.
• Add a cross-platform regression test (test_textExtentLjava_lang_StringI_lineDelimiterVariants) that verifies all three line-ending variants produce the same textExtent height in both advanced and non-advanced mode.

Contributes to #3091

Manual verification

The following snippet renders the same two-line text with \n, \r, and \r\n in both GDI (reference) and GDI+ mode side by side. Before the fix, the CR column in the GDI+ row shows both lines collapsed onto one line. After the fix all six cells look identical.

The 中 character is included in the GDI+ strings to force the drawTextGDIP() path via useGDIP() (it has no glyph in Courier New). It appears at the end of line 2 and can be ignored.

import org.eclipse.swt.*;
import org.eclipse.swt.graphics.*;
import org.eclipse.swt.layout.*;
import org.eclipse.swt.widgets.*;

public class SnippetGdipLineEndings {

    private static final String GDIP_TRIGGER = "中";

    private static final String[][] CASES = {
        { "LF  (\n)",     "Line1\nLine2",   "Line1\nLine2 "   + GDIP_TRIGGER },
        { "CR  (\r)",     "Line1\rLine2",   "Line1\rLine2 "   + GDIP_TRIGGER },
        { "CRLF (\r\n)", "Line1\r\nLine2", "Line1\r\nLine2 " + GDIP_TRIGGER },
    };

    public static void main(String[] args) {
        Display display = new Display();
        Shell shell = new Shell(display);
        shell.setText("GDI+ line-ending test");
        shell.setSize(660, 340);
        shell.setLayout(new FillLayout());

        Canvas canvas = new Canvas(shell, SWT.DOUBLE_BUFFERED);
        Font font = new Font(display, "Courier New", 11, SWT.NORMAL);
        canvas.setFont(font);

        canvas.addPaintListener(e -> {
            GC gc = e.gc;
            gc.setFont(font);
            int colW = 200, rowH = 120, labelH = 18, margin = 10;

            for (int i = 0; i < CASES.length; i++) {
                gc.setAdvanced(false);
                gc.drawText(CASES[i][0], margin + i * colW, 5, SWT.DRAW_TRANSPARENT);
            }

            gc.setAdvanced(false);
            gc.drawText("GDI (reference):", margin, labelH + 8, SWT.DRAW_TRANSPARENT);
            for (int i = 0; i < CASES.length; i++) {
                int x = margin + i * colW, y = labelH + 24;
                gc.setAdvanced(false);
                gc.drawText(CASES[i][1], x, y, SWT.DRAW_DELIMITER | SWT.DRAW_TRANSPARENT);
                gc.drawRectangle(x - 2, y - 2, colW - 16, rowH - labelH - 24);
            }

            int row2Y = rowH + 10;
            gc.setAdvanced(false);
            gc.drawText("GDI+ (drawTextGDIP):", margin, row2Y + labelH + 8, SWT.DRAW_TRANSPARENT);
            gc.setAdvanced(true);
            for (int i = 0; i < CASES.length; i++) {
                int x = margin + i * colW, y = row2Y + labelH + 24;
                gc.drawText(CASES[i][2], x, y, SWT.DRAW_DELIMITER | SWT.DRAW_TRANSPARENT);
            }
            gc.setAdvanced(false);
            for (int i = 0; i < CASES.length; i++) {
                int x = margin + i * colW, y = row2Y + labelH + 24;
                gc.drawRectangle(x - 2, y - 2, colW - 16, rowH - labelH - 24);
            }
        });

        shell.open();
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) display.sleep();
        }
        font.dispose();
        display.dispose();
    }
}

[github-actions]

Test Results

  182 files  ±0    182 suites  ±0   25m 28s ⏱️ - 1m 17s
4 731 tests +1  4 708 ✅ +1   23 💤 ±0  0 ❌ ±0 
6 860 runs  +6  6 697 ✅ +6  163 💤 ±0  0 ❌ ±0 

Results for commit 5e3cee1. ± Comparison against base commit c42bbab.