Using themes

A theme (or style theme) is a definition of the "look & feel" of a table. It doesn't affect the structure of the table such as the size of the table or how many columns or rows a cell spans. It is practical shortcut when many tables should be displayed in the same style. It allows the compact specification of the table by applying a theme to the table instead of having to call multiple functions to achieve the same thing. In addition, if the design should be changed there is only one place to update instead of for each table.

A theme can also be serialized to and from a file/string buffer

A theme controls the following aspects of a table

• The content and label text style
• The header and title text style
• The inner and outer border style
• The usage (or not) of labels and whether the shorter label grind lines should be used
• If a header row should be used or not
• If a title should be used or not

if you have multiple table in a document it is possible to create a table theme which consists of some core styling of a table that can be reused.

Note

By design any specific settings for individual cells is not saved in a theme as a theme can be applied to any table regardless of the specific table structure.

All information for a theme is encapsulated in the hpdftbl_theme structure.

This structure can be set up manually and then applied to a table. However, the recommended way is to first use the "theme getter" function to get the default theme and then modify this default theme as needed since it allows you to only have to update the parts affected by a change.

The functions to work with a theme are :

API	Description
hpdftbl_apply_theme()	Apply the given theme to a table
hpdftbl_get_default_theme()	Get the default theme into a new allocated structure
hpdftbl_destroy_theme()	Free the memory used by a theme
hpdftbl_get_theme()	Extract a theme from specified table
hpdftbl_theme_dump()	Serialize a theme to a file
hpdftbl_theme_dumps()	Serialize a theme to a string buffert
hpdftbl_theme_load()	Load a serialized theme from file
hpdftbl_theme_loads()	Load a serialized theme from a string buffert

It is the responsibility of the user of the library to destroy the theme structure by ensuring that hpdftbl_destroy_theme() is called when a theme goes out of scope.

The default font styles for the default theme are shown in table 1.

Style	Font	Size	Color	Background	Alignment
content	HPDF_FF_COURIER	10	Black	White	Left
label	HPDF_FF_TIMES_ITALIC	9	Dark gray	White	Left
header	HPDF_FF_HELVETICA_BOLD	10	Black	Light gray	Center
title	HPDF_FF_HELVETICA_BOLD	11	Black	Light gray	Left

Table 1: Default font styles.

 

Theme parameter	Default value
use_labels	FALSE
use_label_grid_style	FALSE
use_header_row	FALSE
use_zebra	FALSE

Table 2: Default table structure parameters.

 

Border	Color	Width (pt)
inner_border	Grey	0.7
outer_grid	Dark Grey	1.0

Table 3: Default border parameters.

Example of serializing theme and table

In tut_ex41.c an example ofmhow to read a theme and table back from their serialized representation can be found as also shown below.

hpdftbl_t tbl = calloc(1, sizeof (struct hpdftbl));
hpdftbl_theme_t theme;
 
if(0 == hpdftbl_load(tbl, "tests/tut_ex41.json")  ) {
 
    if(0 == hpdftbl_theme_load(&theme, "tests/tut41_theme.json")) {
        hpdftbl_apply_theme(tbl, &theme);
        hpdftbl_stroke_pos(pdf_doc, pdf_page, tbl);
    } else {
        fprintf(stderr,"%s\n","Failed to load 'tests/default_theme.json'\n");
        exit(1);
    }
} else {
    fprintf(stderr,"%s\n","Failed to load 'tests/tut_ex41.json'\n");
    exit(1);
}