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Practical Programming in Tcl & Tk, Third Edition
By Brent B. Welch

Table of Contents
Chapter 41.  Window Managers and Window Information

The tk Command

The tk command provides a few miscellaneous entry points into the Tk library. The appname operation is used to set or query the application name used with the Tk send command. If you define a new name and it is already in use by another application, (perhaps another instance of yourself), then a number is appended to the name (e.g., #2, #3, and so on). This is the syntax of the command:

tk appname ?name?

Fonts, canvas items, and widget sizes use screen units that are pixels, points, centimeters, millimeters, or inches. There are 72 points per inch. The tk scaling command, which was added in Tk 8.0, is used to set or query the mapping between pixels and points. A scale of 1.0 results in 72 pixels per inch. A scale of 1.25 results in 90 pixels per inch. This gives accurate sizes on a 90 dpi screen or it makes everything 25% larger on a 72 dpi screen. Changing the scale only affects widgets created after the change. This is the syntax of the command:

tk scaling ?num?

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