Calendar - Layout strings formatting with C++ binding

In this simple example, we'll explain how to format the labels displaying month and year, and also set weekday names.

The first part consists of including the headers. In this case we are only working with the Elementary C++ binding and thus we need only to include him.

#include <Elementary.hh>

If necessary the C and/or the C++ headers should be include here as well.

Now we will jump to the actual code and later explain the function to make this tutorial more didactical.

We must set the elm_policy, which defines for a given policy group/identifier a new policy's value, respectively. In this example the only policy we need to set a value for is ELM_POLICY_QUIT, possibles values for it are:

elm_main (int argc, char *argv[])

As you can see, the policy we chose was to quit when the last win is hidden as opose to examples with the C bindings where we perpetually set it to quit when last win was closed. This changed was necessary because in C++ binding as the elm mainloop stop running all object are destroyed, references are unreferenced and events are stopped at ELM_MAIN().

See also
For more details consult elm_policy_set

Next step is creating an Elementary window, in this example we use the C++ binding method with the elm_win_util_standard_add that is a elm_win_legacy function, better explained below. And then we set the autohide state for it.

elm_win_util_standard_add (const char *name, const char *tittle) Adds a window object with standard setup. Parameters:

This creates a window but also puts in a standard background with elm_bg_add(), as well as setting the window title to title. The window type created is of type ELM_WIN_BASIC, with the NULL as the parent widget. Returns the created object or NULL on failure.

The autohide works similarly to autodel, automatically handling "delete,request" signals when set to true, with the difference that it will hide the window, instead of destroying it.

It is specially designed to work together with ELM_POLICY_QUIT_LAST_WINDOW_HIDDEN which allows exiting Elementary's main loop when all the windows are hidden.

win.title_set("Calendar Layout Formatting Example");

autodel and autohide are not mutually exclusive. The window will be destructed if both autodel and autohide is set to EINA_TRUE or true.

Now let's create the calendar with the C++ binding method, passing our window object as parent.

::elm::calendar cal(efl::eo::parent = win);

The function size_hint_weight_set for C++ bindings originated from C bindings function evas_object_size_hint_weight_set, that is EFL Evas type function. With this function we set the hints for an object's weight. The parameters are:

This is not a size enforcement in any way, it's just a hint that should be used whenever appropriate. This is a hint on how a container object should resize a given child within its area.

Containers may adhere to the simpler logic of just expanding the child object's dimensions to fit its own (see the EVAS_HINT_EXPAND helper weight macro in the EFL Evas Documentation) or the complete one of taking each child's weight hint as real weights to how much of its size to allocate for them in each axis. A container is supposed to, after normalizing the weights of its children (with weight hints), distribute the space it has to layout them by those factors – most weighted children get larger in this process than the least ones.

cal.size_hint_weight_set(EVAS_HINT_EXPAND, EVAS_HINT_EXPAND);

Default weight hint values are 0.0, for both axis.

Now we add the calendar as a resize-object to win informing that when the size of the win changes so should the calendar's size.


To format month and year labels, we need to create a callback function to create a string given the selected time, declared under a struct tm .

struct tm , declared on time.h, is a structure composed by nine integers:

Glib version has 2 additional fields.

For our function _format_month_year , only stuff that matters are tm_mon and tm_year. But we don't need to access it directly, since there are nice functions to format date and time, as strftime.

We will get abbreviated month (b) and year (y) (check strftime manpage for more) in our example:

static char *
_format_month_year(struct tm *format_time)
char buf[32];
if (!strftime(buf, sizeof(buf), "%b %y", format_time)) return NULL;
return strdup(buf);

We need to alloc the string to be returned, and calendar widget will free it when it's not needed, what is done by strdup.

So let's register our callback to calendar object:


To set weekday names, we should declare them as an array of strings:

const char *weekdays[] =
"S", "M", "T", "W", "T", "F", "S"

And then set them to calendar:


Finally we just have to make the calendar and window visible and then start the elm mainloop, starting to handle events and drawing operations.

Our example will look like this:


See the full source code here.