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move command window to separate file and other refactoring
author John W. Eaton <jwe@octave.org>
date Thu, 23 May 2019 12:36:26 -0400
parents 52c033864347
children bfa9aaa2d608
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1 To build:
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2
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3 qmake calc.pro
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4 make
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5
0
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6 Current terminal widget:
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7
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8 * Run Octave in a separate thread. On unixy, interact through pty.
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9 On Windows systems, use hidden console and mirror contents in Qt
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10 widget.
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11
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12 Octave interpreter sees input directly, same as for normal
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13 terminal application. Good, because no change in the way Octave
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14 accepts and parses input. Bad because GUI is not in control of
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15 input and must arrange to communicate across threads.
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16
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17 Terminal window can (in theory) be used to run other applications
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18 started from the system command (for example). This feature works
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19 well enough for us to use less running as a separate process to
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20 handle paging output, but it doesn't work for all applications.
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21 For example, I am not able to run editors like Emacs or vi in the
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22 GUI terminal window.
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23
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24 To make less work as the pager on Unixy systems, the Octave must
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25 fork, call setsid in the child to detach from the controlling
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26 terminal, and then exec the GUI.
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27
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28 GUI must deal with threads when communicating with the
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29 interpreter.
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30
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31 Proposal:
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32
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33 * GUI terminal widget is in control of input.
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34
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35 Use callback interface for readline to handle command line
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36 editing.
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37
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38 Use push parser to parse lines as they become available. Push
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39 parser will return status of parse, either complete or needing
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40 more input.
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41
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42 Uses the following readline callbacks to manage input and update
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43 the display. We may need more in the future to handle other
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44 features.
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45
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46 rl_getc_function
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47 rl_redisplay_function
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48 rl_completion_display_matches_hook
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49
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50 rl_prep_term_function (do nothing)
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51 rl_deprep_term_function (do nothing)
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52
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53 Call rl_callback_handler_install to setup readlines
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54 callback mode. This sets the initial prompt and provides a pointer
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55 to a function that readline should call when a complete line of
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56 input is available.
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57
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58 Call rl_callback_read_char when a character is available for
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59 readline to handle. We currently store the character to read in a
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60 global value, then rl_get_function returns that character to
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61 readline.
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62
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63 Call rl_callback_handler_remove when shutting down.
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64
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65 To avoid global variables, it would be helpful if we could use
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66 lambda functions/functors as callbacks instead of plain C function
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67 pointers.
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68
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69 Questions:
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70
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71 * With this arrangement, would the interpreter have to run in a
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72 separtae thread?
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73
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74 * Example parser currently computes results
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75 immediately. How do we deal with parsing multiple expressions and
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76 statements with this method?
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77
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78 * Do we need text position markers to keep track of the prompt position
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79 (beginning of current line) when inserting or clearing text?
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80
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81
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82 readline callback functions:
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83
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84 // -- Variable: rl_getc_func_t * rl_getc_function
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85 // If non-zero, Readline will call indirectly through this pointer to
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86 // get a character from the input stream. By default, it is set to
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87 // `rl_getc', the default Readline character input function (*note
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88 // Character Input::).
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89
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90 // -- Variable: rl_voidfunc_t * rl_redisplay_function
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91 // If non-zero, Readline will call indirectly through this pointer to
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92 // update the display with the current contents of the editing buffer.
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93 // By default, it is set to `rl_redisplay', the default Readline
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94 // redisplay function (*note Redisplay::).
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95
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96 // -- Variable: rl_vintfunc_t * rl_prep_term_function
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97 // If non-zero, Readline will call indirectly through this pointer to
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98 // initialize the terminal. The function takes a single argument, an
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99 // `int' flag that says whether or not to use eight-bit characters.
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100 // By default, this is set to `rl_prep_terminal' (*note Terminal
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101 // Management::).
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102
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103 // -- Variable: rl_voidfunc_t * rl_deprep_term_function
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104 // If non-zero, Readline will call indirectly through this pointer to
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105 // reset the terminal. This function should undo the effects of
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106 // `rl_prep_term_function'. By default, this is set to
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107 // `rl_deprep_terminal' (*note Terminal Management::).
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108
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109 // -- Function: void rl_callback_handler_install (const char *prompt,
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110 // rl_vcpfunc_t *lhandler)
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111 // Set up the terminal for readline I/O and display the initial
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112 // expanded value of PROMPT. Save the value of LHANDLER to use as a
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113 // function to call when a complete line of input has been entered.
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114 // The function takes the text of the line as an argument.
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115
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116 // -- Function: void rl_callback_read_char (void)
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117 // Whenever an application determines that keyboard input is
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118 // available, it should call `rl_callback_read_char()', which will
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119 // read the next character from the current input source. If that
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120 // character completes the line, `rl_callback_read_char' will invoke
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121 // the LHANDLER function saved by `rl_callback_handler_install' to
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122 // process the line. Before calling the LHANDLER function, the
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123 // terminal settings are reset to the values they had before calling
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124 // `rl_callback_handler_install'. If the LHANDLER function returns,
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125 // the terminal settings are modified for Readline's use again.
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126 // `EOF' is indicated by calling LHANDLER with a `NULL' line.
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127
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128 // -- Function: void rl_callback_handler_remove (void)
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129 // Restore the terminal to its initial state and remove the line
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130 // handler. This may be called from within a callback as well as
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131 // independently. If the LHANDLER installed by
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132 // `rl_callback_handler_install' does not exit the program, either
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133 // this function or the function referred to by the value of
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134 // `rl_deprep_term_function' should be called before the program
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135 // exits to reset the terminal settings.
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136
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137 // -- Variable: rl_compdisp_func_t * rl_completion_display_matches_hook
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138 // If non-zero, then this is the address of a function to call when
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139 // completing a word would normally display the list of possible
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140 // matches. This function is called in lieu of Readline displaying
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141 // the list. It takes three arguments: (`char **'MATCHES, `int'
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142 // NUM_MATCHES, `int' MAX_LENGTH) where MATCHES is the array of
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143 // matching strings, NUM_MATCHES is the number of strings in that
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144 // array, and MAX_LENGTH is the length of the longest string in that
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145 // array. Readline provides a convenience function,
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146 // `rl_display_match_list', that takes care of doing the display to
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147 // Readline's output stream. That function may be called from this
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148 // hook.