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https://issues.apache.org/jira/browse/PDFBOX-4975?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17205546#comment-17205546
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Richard edited comment on PDFBOX-4975 at 10/1/20, 2:15 PM:
-----------------------------------------------------------
bq. could you outline how you did change PDPageContentStream and how you check
if a font is suitable for a specific character?
Sure this is what I've done
* Create a class that extends {{PDFont}}, say {{PDFontList}}, which is mainly
meant to be a container for a list of fonts
* In {{PDPageContentStream}}, when {{setFont}} is called, check if it's a
{{PDFontList}} and if it is, set it on the {{fontStack}}, set the size (in the
{{PDFontList}} object) and early return
* Also in {{PDPageContentStream}}, when {{showTextInternal}} is called, check
if it's a {{PDFontList}}, if it is then
** For each character in the text
*** For each font
**** Try to encode the character using the font, if it works then call
{{setFont}} and {{showText}} and early return from this for loop (going to the
next character)
* At the end call {{setFont}} with the {{PDFontList}} and early return
So you create an instance of {{PDFontList}} with the fonts you want and set
{{PDPageContentStream}} to use this font. Then anything using this instance,
calling its {{PDPageContentStream.showText}} or
{{PDPageContentStream.showTextWithPositioning}} will automatically try all
fonts.
{{PDFontList}} also has a font descriptor and a few methods which return the
max/min value of the fonts it has (e.g. max ascent) but I just set those as I
needed them.
was (Author: mealing):
bq. could you outline how you did change PDPageContentStream and how you check
if a font is suitable for a specific character?
Sure this is what I've done
* Create a class that extends {{PDFont}}, say {{PDFontList}}, which is mainly
meant to be a container for a list of fonts
* In {{PDPageContentStream}}, when {{setFont}} is called, check if it's a
{{PDFontList}} and if it is, set it on the {{fontStack}}, set the size (in the
{{PDFontList}} object) and early return
* Also in {{PDPageContentStream}}, when {{showTextInternal}} is called, check
if it's a {{PDFontList}}, if it is then
** For each character in the text
*** For each font
**** Try to encode the character using the font, if it works then call
{{setFont}} and {{showText}} and early return from this for loop (going to the
next character)
* At the end call {{setFont}} with the {{PDFontList}} and early return
So you create an instance of {{PDFontList}} with the fonts you want and set
{{PDPageContentStream}} to use this font. Then anything using this instance,
calling its {{PDPageContentStream.showText}} or
{{PDPageContentStream.showTextWithPositioning} } will automatically try all
fonts.
{{PDFontList}} also has a font descriptor and a few methods which return the
max/min value of the fonts it has (e.g. max ascent) but I just set those as I
needed them.
> Make PDPageContentStream non-final
> -----------------------------------
>
> Key: PDFBOX-4975
> URL: https://issues.apache.org/jira/browse/PDFBOX-4975
> Project: PDFBox
> Issue Type: Wish
> Reporter: Richard
> Priority: Major
>
> Currently {{PDPageContentStream}} is final.
> There are some situations where it would be useful to define our own
> {{PDPageContentStream}}.
> For example, in my use-case I want to be able to try multiple fonts in case
> the characters in the text are not all in one font. The library I'm using
> accepts {{PDPageContentStream}} instances, so it would be much easier to pass
> a subclass of {{PDPageContentStream}} with the desired behavior rather than
> overhaul the library itself.
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