Tk_AllocColorFromObj(3)

✨ Tk_AllocColorFromObj — the color database page ✨

okay bestie, welcome to Tk_AllocColorFromObj(3), a Tk Library Procedures moment 💖 this is the whole girl-gang of color functions and they all live in the Tk library, iykyk.

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🌈 NAME 🌈

Tk_AllocColorFromObj, Tk_GetColor, Tk_GetColorFromObj, Tk_GetColorByValue, Tk_NameOfColor, Tk_FreeColorFromObj, Tk_FreeColor — maintain database of colors 💅

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🎀 SYNOPSIS 🎀

#include <tk.h>

XColor *
Tk_AllocColorFromObj(interp, tkwin, objPtr)

XColor *
Tk_GetColor(interp, tkwin, name)

XColor *
Tk_GetColorFromObj(tkwin, objPtr)

XColor *
Tk_GetColorByValue(tkwin, prefPtr)

const char *
Tk_NameOfColor(colorPtr)

GC
Tk_GCForColor(colorPtr, drawable)

Tk_FreeColorFromObj(tkwin, objPtr)

Tk_FreeColor(colorPtr)

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🦋 ARGUMENTS 🦋

• Tcl_Interp *interp (in) — the interpreter we use when we gotta report an error, periodt.
• Tk_Window tkwin (in) — the token for the window where this color is gonna be used.
• Tcl_Obj *objPtr (in/out) — the string value describes the color you want; the internal rep gets modified so it can cache a pointer to the corresponding (XColor *). lowkey a glow-up moment for that obj.
• const char *name (in) — same as objPtr except the color description comes in as a string, and the resulting (XColor *) is not cached. no caching bestie, sorry.
• XColor *prefPtr (in) — tells you the red, green, and blue intensities of the color you're wishing for ✨
• XColor *colorPtr (in) — pointer to X color info. It must have been allocated by a previous call to Tk_AllocColorFromObj, Tk_GetColor or Tk_GetColorByValue — except when you're passing it to Tk_NameOfColor, which is the one exception. don't be out here passing random pointers, that's not the vibe.
• Drawable drawable (in) — the drawable where the resulting graphics context is gonna be used. It must have the same screen and depth as the window the color was allocated for. same screen, same depth, no exceptions 💀

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💖 DESCRIPTION 💖

These procedures manage the colors being used by a Tk application. They let colors be shared whenever possible, so colormap space is preserved, and when colormap space is all used up they pick the closest available colors. recycling queen behavior, honestly 👑

Given a textual description of a color, Tk_AllocColorFromObj locates a pixel value that may be used to render that color in a particular window. The color you want is specified with a value whose string value must have one of these forms:

• colorname — literally any of the valid textual names for a color defined in the server's color database file, like red or PeachPuff. 🍑 iconic names only.
• #RGB
• #RRGGBB
• #RRRGGGBBB
• #RRRRGGGGBBBB — a numeric spec of the red, green, and blue intensities to use to display the color. Each R, G, or B is a single hexadecimal digit. These four forms let you specify colors with 4-bit, 8-bit, 12-bit or 16-bit values. When fewer than 16 bits are provided for each color, they represent the most significant bits of the color, while the lower unfilled bits get repeatedly replicated from the available higher bits. For example, #3a7 is the same as #3333aaaa7777. the way that math just works out… 🧮✨

Tk_AllocColorFromObj returns a pointer to an XColor structure; that structure indicates the exact intensities of the allocated color (which may differ slightly from the ones you requested, depending on the limitations of the screen) and a pixel value that may be used to draw with the color in tkwin. If an error occurs in Tk_AllocColorFromObj (like an unknown color name, oops) then NULL is returned and an error message is stored in interp's result if interp is not NULL. If the colormap for tkwin is full, Tk_AllocColorFromObj will use the closest existing color in the colormap. And Tk_AllocColorFromObj caches information about the return value in objPtr, which speeds up future calls to procedures such as Tk_AllocColorFromObj and Tk_GetColorFromObj. cache queen 🫶

Tk_GetColor is identical to Tk_AllocColorFromObj except that the description of the color is specified with a string instead of a value. This prevents Tk_GetColor from caching the return value, so Tk_GetColor is less efficient than Tk_AllocColorFromObj. it's giving slow cousin energy, but valid.

Tk_GetColorFromObj returns the token for an existing color, given the window and description used to create that color. Tk_GetColorFromObj does not actually create the color; the color must already have been created with a previous call to Tk_AllocColorFromObj or Tk_GetColor. The return value is cached in objPtr, which speeds up future calls to Tk_GetColorFromObj with the same objPtr and tkwin.

Tk_GetColorByValue is similar to Tk_GetColor except that the desired color is indicated with the red, green, and blue fields of the structure pointed to by colorPtr.

This package maintains a database of all the colors currently in use. If the same color is requested multiple times from Tk_GetColor or Tk_AllocColorFromObj (e.g. by different windows), or if the same intensities are requested multiple times from Tk_GetColorByValue, then existing pixel values will be re-used. Re-using an existing pixel avoids any interaction with the window server, which makes the allocation much more efficient. These procedures also provide a portable interface that works across all platforms. For this reason, you should generally use Tk_AllocColorFromObj, Tk_GetColor, or Tk_GetColorByValue instead of lower level procedures like XAllocColor. bestie, stay on the high road, use the nice interface 💅

Since different calls to this package may return the same shared pixel value, callers should never change the color of a pixel returned by the procedures. If you need to change a color value dynamically, you should use XAllocColorCells to allocate the pixel value for the color.

🚨 do NOT touch the shared pixel, that's a friendship-ending move. it's shared. it's not yours. if you need your own, XAllocColorCells is right there.

The procedure Tk_NameOfColor is roughly the inverse of Tk_GetColor. If its colorPtr argument was created by Tk_AllocColorFromObj or Tk_GetColor then the return value is the string that was used to create the color. If colorPtr was created by a call to Tk_GetColorByValue, or by any other mechanism, then the return value is a string that could be passed to Tk_GetColor to return the same color. Note: the string returned by Tk_NameOfColor is only guaranteed to persist until the next call to Tk_NameOfColor. so screenshot it mentally, it expires fast 😭

Tk_GCForColor returns a graphics context whose foreground field is the pixel allocated for colorPtr and whose other fields all have default values. This provides an easy way to do basic drawing with a color. The graphics context is cached with the color and will exist only as long as colorPtr exists; it is freed when the last reference to colorPtr is freed by calling Tk_FreeColor. ride or die, until the free 💀

When a color is no longer needed Tk_FreeColorFromObj or Tk_FreeColor should be called to release it. For Tk_FreeColorFromObj the color to release is specified with the same information used to create it; for Tk_FreeColor the color to release is specified with a pointer to its XColor structure. There should be exactly one call to Tk_FreeColorFromObj or Tk_FreeColor for each call to Tk_AllocColorFromObj, Tk_GetColor, or Tk_GetColorByValue. one in, one out, that's the whole balance of the universe ⚖️

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🌸 KEYWORDS 🌸

color, intensity, value, pixel value

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okay that's the whole page, you ate that 🍓 this was Tk version 8.1, dated Tk_AllocColorFromObj(3), and it's giving very much Tk library classic. go allocate responsibly bestie 💜🦋✨