Something strange with positioning text with custom font in Itext7 - java-8

Question

I'm working on a program that creates several pdf docs and puts different text in the same location in them.
Text should be placed in a particular area and if it doesn't fit it in width it should wrap. It also has a custom font and may be differently aligned in that area. It should be Vertically aligned to Top because when the area is laid out for three lines and I has only one, it should appear on the top. Finally, I need to preserve leading on the level of font-size.
It is important to be precise in text positioning (e.g. I need an upper left corner of "H" from "Hello world" to appear definitely at 0, 100).
Now, I'm using
canvas.showTextAligned(paragraph, 0, 300,
TextAlignment.valueOf(alignment),
VerticalAlignment.TOP);
However, when I try to implement it with different fonts it has a various offset from desired y = 300. Moreover, offset differ from font to font. For Helvetica (everywhere 50 fontSize is used) offset is about 13 px, for Oswald about 17 px and for SedgwickAveDisplay it is massive 90 px.
I added borders to paragraph for debugging purpose and things become more strange.
Helvetica:
SedgwickAveDisplay:
The full snippet of my code to create pdf is below:
public byte[] createBadgeInMemory(int i) throws IOException {
ByteArrayOutputStream out = new ByteArrayOutputStream();
PdfDocument newPdf = new PdfDocument(new PdfWriter(out));
srcPdf.copyPagesTo(1,1,newPdf);
PdfPage page = newPdf.getFirstPage();
PdfCanvas pdfCanvas = new PdfCanvas(page);
Canvas canvas = new Canvas(pdfCanvas, newPdf, pageSize);
File defaultFont = new File("src/main/resources/fonts/Helvetica.otf");
PdfFont font = PdfFontFactory
.createFont(fontPath == null ? defaultFont.getAbsolutePath() : fontPath,
PdfEncodings.IDENTITY_H, true);
String value = "Example word";
Paragraph paragraph = new Paragraph(value);
float textWidth = font.getWidth("Example", 50);
paragraph.setWidth(textWidth);
switch (alignment) {
case("CENTER"):
textWidth /= 2;
break;
case("RIGHT"):
break;
default:
textWidth = 0;
break;
}
paragraph.setFont(font)
.setFontSize(fontSize)
.setFixedLeading(fontSize)
.setFontColor(new DeviceRgb(red, green, blue))
.setMargin(0)
.setPadding(0);
paragraph.setBorderTop(new DashedBorder(Color.BLACK, 0.5f))
.setBorderBottom(new DashedBorder(Color.BLACK, 0.5f))
.setBorderRight(new DashedBorder(Color.BLACK, 0.5f));
paragraph.setHyphenation(new HyphenationConfig(0,
"Example".length()));
canvas.showTextAligned(paragraph,
0 + textWidth,
300,
TextAlignment.valueOf(alignment),
VerticalAlignment.TOP);
newPdf.close();
return out.toByteArray();
}
I also tried variant from here, but for some reason text inside rectangle cuts out at some point (for instance, if I have area width 100px and text snippet I put in that I know occupies exactly 100 px (with the help of font.getWidth(value)), I have my text cut at nearly 80 px).
I also haven't found a way to align text inside a rectangle.
This is the result with Rectangle. A solid border is Rectangle border. As you can see it cuts letter "t" in "Redundant". It also should contain "word" on the second line, but it doesn't.
I copied code from an example.
I need your help. What am I doing wrong or may be there is another way to layout text in particular area with alignment and font?
Thank you in advance.
Update 21.09.17
Also tried variant from this question with SedgwickAveDisplay:
paragraph.setHorizontalAlignment(HorizontalAlignment.LEFT);
paragraph.setVerticalAlignment(VerticalAlignment.TOP);
paragraph.setFixedPosition( 0, 300 - textHeight, "Example".length());
doc.add(paragraph);
The result is the same as on the second screenshot.

Answer 1

This is a font-specific problem. iText guesses information about font glyphs, namely the bboxes incorrectly.
There is a quick and dirty method to adjust this behavior. You can create a custom renderer for text and adjust the calculated positions in it. An example of such a class would be as follows:
class CustomTextRenderer extends TextRenderer {
private CustomTextRenderer(Text text) {
super(text);
}
#Override
public LayoutResult layout(LayoutContext layoutContext) {
LayoutResult result = super.layout(layoutContext);
Rectangle oldBbox = this.occupiedArea.getBBox().clone();
// you can also make the height more than font size or less if needed
this.occupiedArea.setBBox(oldBbox.moveUp(oldBbox.getHeight() - fontSize).setHeight(fontSize));
yLineOffset = fontSize * 0.8f; // here you config the proportion of the ascender
return result;
}
#Override
public IRenderer getNextRenderer() {
return new CustomTextRenderer((Text) modelElement);
}
}
In order that new rendering logic to be applied, you have to use it in the following way:
Text text = new Text(value);
text.setNextRenderer(new CustomTextRenderer(text));
Paragraph paragraph = new Paragraph(text);
Please note that you have to be very careful with this kind of low-level layouting, be aware of you are doing and use this as seldom as possible.

Answer 2

Finally, I created a variant that worked for me.
pdfCanvas.beginText()
.setFontAndSize(font, fontSize)
.setLeading(fontSize)
.moveText(0, 300);
numberOfLines = 0;
sumOfShifts = 0;
float maxWidth = computeStringWidth("Exaxple");
String[] words = value.split("\\s");
StringBuilder line = new StringBuilder();
line.append(words[0]);
float spaceWidth = computeStringWidth(" ") ;
float lineWidth;
for (int index = 1; index < words.length; index++) {
String word = words[index];
float wordWidth = computeStringWidth(word) ;
lineWidth = computeStringWidth(line.toString()) ;
if (lineWidth + spaceWidth + wordWidth <= maxWidth) {
line.append(" ").append(word);
} else {
showTextAligned(alignment, pdfCanvas, line.toString(), lineWidth, maxWidth);
line.delete(0, line.length());
line.append(word);
}
}
if(line.length() != 0) {
lineWidth = computeStringWidth(line.toString()) ;
showTextAligned(alignment, pdfCanvas, line.toString(), lineWidth, maxWidth);
}
pdfCanvas.endText();
As computeStringWidth(String str) I used
Toolkit.getToolkit().getFontLoader().computeStringWidth(String str, Font font);
from import com.sun.javafx.tk.Toolkit with Font from javafx.scene.text.Font. I've chosen it because I use it in other parts of my app.
showTextAligned(...) is my own method that looks this way:
private void showTextAligned(String alignment,
PdfCanvas pdfCanvas,
String line,
float lineWidth,
float maxWidth) {
switch (alignment) {
case "CENTER": {
float shift = (maxWidth - lineWidth) / 2 - sumOfShifts;
pdfCanvas.moveText(shift, 0);
if(numberOfLines == 0) pdfCanvas.showText(line);
else pdfCanvas.newlineShowText(line);
numberOfLines++;
sumOfShifts += shift;
break;
}
case "RIGHT": {
float shift = maxWidth - lineWidth - sumOfShifts;
pdfCanvas.moveText(shift, 0);
if(numberOfLines == 0) pdfCanvas.showText(line);
else pdfCanvas.newlineShowText(line);
numberOfLines++;
sumOfShifts += shift;
break;
}
default:
pdfCanvas.moveText(0, 0);
if(numberOfLines == 0) pdfCanvas.showText(line);
else pdfCanvas.newlineShowText(line);
numberOfLines++;
break;
}
}
In my project, I used my variant, because it gives me an opportunity to work with hyphenation deeper (for instance, I can in future add functionality to avoid putting prepositions as a last word in the line).