The ascent member is set to the maximum of the ascent metrics of all characters in the string. The descent member is set to the maximum of the descent metrics. The width member is set to the sum of the character-width metrics of all characters in the string. For each character in the string, let W be the sum of the character-width metrics of all characters preceding it in the string. Let L be the left-side-bearing metric of the character plus W. Let R be the right-side-bearing metric of the character plus W. The lbearing member is set to the minimum L of all characters in the string. The rbearing member is set to the maximum R.
For fonts defined with linear indexing rather than 2-byte matrix indexing, each _X_C_h_a_r_2_b structure is interpreted as a 16-bit number with byte1 as the most significant byte. If the font has no defined default character, undefined characters in the string are taken to have all zero metrics.
The _X_Q_u_e_r_y_T_e_x_t_E_x_t_e_n_t_s and _X_Q_u_e_r_y_T_e_x_t_E_x_t_e_n_t_s_1_6 functions return the bounding box of the specified 8-bit and 16-bit character string in the specified font or the font contained in the specified GC. These functions query the X server and, therefore, suffer the round-trip overhead that is avoided by _X_T_e_x_t_E_x_t_e_n_t_s and _X_T_e_x_t_E_x_t_e_n_t_s_1_6. Both functions return a _X_C_h_a_r_S_t_r_u_c_t structure, whose members are set to the values as follows.
The ascent member is set to the maximum of the ascent metrics of all characters in the string. The descent member is set to the maximum of the descent metrics. The width member is set to the sum of the character-width metrics of all characters in the string. For each character in the string, let W be the sum of the character-width metrics of all characters preceding it in the string. Let L be the left-side-bearing metric of the character plus W. Let R be the right-side-bearing metric of the character plus W. The lbearing member is set to the minimum L of all characters in the string. The rbearing member is set to the maximum R.
For fonts defined with linear indexing rather than 2-byte matrix indexing, each _X_C_h_a_r_2_b structure is interpreted as a 16-bit number with byte1 as the most significant byte. If the font has no defined default character, undefined characters in the string are taken to have all zero metrics.
Characters with all zero metrics are ignored. If the font has no defined default_char, the undefined characters in the string are also ignored.
_X_Q_u_e_r_y_T_e_x_t_E_x_t_e_n_t_s and _X_Q_u_e_r_y_T_e_x_t_E_x_t_e_n_t_s_1_6 can generate _B_a_d_F_o_n_t and _B_a_d_G_C errors.