Automatically resize active terminal to not overlap with keyboard

.gitignore

@@ -1,2 +1,3 @@
-*.o
 buffyboard
+*.o
+.vscode

Makefile

@@ -23,7 +23,7 @@ CFLAGS ?= -O3 -g0 -I$(LVGL_DIR)/ -Wall -Wshadow -Wundef -Wmissing-prototypes -Wn
 LDFLAGS ?= -lm -linput
 BIN = buffyboard
 
-MAINSRC = ./cursor.c ./layout.c ./libinput_multi.c ./main.c ./montserrat_extended_32.c ./sq2lv_layouts.c ./uinput_device.c
+MAINSRC = ./cursor.c ./layout.c ./libinput_multi.c ./main.c ./montserrat_extended_32.c ./sq2lv_layouts.c ./terminal.c ./uinput_device.c
 
 include $(LVGL_DIR)/lvgl/lvgl.mk
 include $(LVGL_DIR)/lv_drivers/lv_drivers.mk

README.md

@@ -15,11 +15,11 @@ While partially usable, buffyboard currently still is a work in progress.
 - Multi-layer keyboard layout including lowercase letters, uppercase letters, numbers and selected symbols (based on top three layers of [squeekboard's US terminal layout])
 - Key chords with one or more modifiers terminated by a single non-modifier (e.g. `CTRL-c`)
 - Highlighting of active modifiers
+- Automatic resizing (and later reset) of active VT to prevent overlap with keyboard
 
 ## To do
 
 - Show keyboard at the bottom of the screen instead of at the top (just need to set the offset once [lvgl/lv_drivers#164] is merged)
-- Resize VT screen size to not overlap with keyboard
 - Support different screen rotations
 - Eliminate `libinput_multi.[ch]` once support for multiple input devices has been upstreamed to [lv_drivers] (see [lvgl/lv_drivers#151])
 - Add remaining layers from [squeekboard's US terminal layout] (symbols and actions)

main.c

@@ -22,6 +22,7 @@
 #include "layout.h"
 #include "libinput_multi.h"
 #include "sq2lv_layouts.h"
+#include "terminal.h"
 #include "uinput_device.h"
 
 #include "lvgl/lvgl.h"
@@ -29,6 +30,7 @@
 #include "lv_drivers/indev/libinput_drv.h"
 
 #include <limits.h>
+#include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <unistd.h>
@@ -47,6 +49,7 @@ LV_FONT_DECLARE(montserrat_extended_32);
  * Static variables
  */
 
+static bool resize_terminals = false;
 static lv_obj_t *keyboard = NULL;
 static lv_style_t style_text_normal;
 
@@ -55,6 +58,20 @@ static lv_style_t style_text_normal;
  * Static prototypes
  */
 
+/**
+ * Handle termination signals sent to the process.
+ *
+ * @param signum the signal's number
+ */
+static void sigaction_handler(int signum);
+
+/**
+ * Callback for the terminal resizing timer.
+ *
+ * @param timer the timer object
+ */
+static void terminal_resize_timer_cb(lv_timer_t *timer);
+
 /**
  * Set the UI theme.
  * 
@@ -91,6 +108,19 @@ static void pop_checked_modifier_keys(lv_obj_t *keyboard);
  * Static functions
  */
 
+static void sigaction_handler(int signum) {
+    if (resize_terminals) {
+        bb_terminal_reset_all();
+    }
+    exit(0);
+}
+
+static void terminal_resize_timer_cb(lv_timer_t *timer) {
+    if (resize_terminals) {
+        bb_terminal_shrink_current();
+    }
+}
+
 static void set_theme(bool is_dark) {
     lv_theme_default_init(NULL, lv_palette_main(LV_PALETTE_BLUE), lv_palette_main(LV_PALETTE_CYAN), is_dark, &montserrat_extended_32);
 }
@@ -195,8 +225,21 @@ static void keyboard_draw_part_begin_cb(lv_event_t *event) {
  * Main
  */
 
-int main(void)
-{
+int main(void) {
+    /* Prepare for terminal resizing and reset */
+    resize_terminals = bb_terminal_init(2.0f / 3.0f);
+    if (resize_terminals) {
+        /* Clean up on termination */
+        struct sigaction action;
+        memset(&action, 0, sizeof(action));
+        action.sa_handler = sigaction_handler;
+        sigaction(SIGINT, &action, NULL);
+        sigaction(SIGTERM, &action, NULL);
+
+        /* Resize current terminal */
+        bb_terminal_shrink_current();
+    }
+
     /* Set up uinput device */
     if (!bb_uinput_device_init(sq2lv_unique_scancodes, sq2lv_num_unique_scancodes)) {
         return 1;
@@ -293,6 +336,9 @@ int main(void)
     /* Apply default keyboard layout */
     bb_layout_switch_layout(keyboard, SQ2LV_LAYOUT_TERMINAL_US);
 
+    /* Start timer for periodically resizing terminals */
+    lv_timer_create(terminal_resize_timer_cb, 1000,  NULL);
+
     /* Run lvgl in "tickless" mode */
     while(1) {
         lv_task_handler();

terminal.c

@@ -0,0 +1,294 @@
+/**
+ * Copyright 2021 Johannes Marbach
+ *
+ * This file is part of buffyboard, hereafter referred to as the program.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+#include "terminal.h"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <math.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+
+#include <linux/vt.h>
+
+#include <sys/ioctl.h>
+
+
+/**
+ * Static variables
+ */
+
+static int current_fd = -1;
+static int current_vt = -1;
+static bool resized_vts[MAX_NR_CONSOLES];
+static float height_factor = 1;
+
+/**
+ * Static prototypes
+ */
+
+/**
+ * Close the current file descriptor and reopen /dev/tty0.
+ * 
+ * @return true if opening was successful, false otherwise
+ */
+static bool reopen_current_terminal(void);
+
+/**
+ * Close the current file descriptor.
+ */
+static void close_current_terminal(void);
+
+/**
+ * Get the currently active virtual terminal.
+ * 
+ * @return number of the active VT (e.g. 7 for /dev/tty7)
+ */
+static int get_active_terminal(void);
+
+/**
+ * Retrieve a terminal's size.
+ * 
+ * @param fd TTY file descriptor
+ * @param size pointer to winsize struct for writing the size into
+ * @return true if the operation was successful, false otherwise. On failure, errno will be set
+ * to the value set by the failed system call.
+ */
+static bool get_terminal_size(int fd, struct winsize *size);
+
+/**
+ * Update a terminal's size.
+ * 
+ * @param fd TTY file descriptor
+ * @param size pointer to winsize struct for reading the new size from
+ * @return true if the operation was successful, false otherwise. On failure, errno will be set
+ * to the value set by the failed system call.
+ */
+static bool set_terminal_size(int fd, struct winsize *size);
+
+/**
+ * Shrink the height of a terminal by the current factor.
+ * 
+ * @param fd TTY file descriptor
+ * @return true if the operation was successful, false otherwise
+ */
+static bool shrink_terminal(int fd);
+
+/**
+ * Reset the height of a terminal to the maximum.
+ * 
+ * @param fd TTY file descriptor
+ * @param size pointer to winsize struct for writing the final size into
+ * @return true if the operation was successful, false otherwise
+ */
+static bool reset_terminal(int fd, struct winsize *size);
+
+
+/**
+ * Static functions
+ */
+
+static bool reopen_current_terminal(void) {
+    close_current_terminal();
+
+    current_fd = open("/dev/tty0", O_RDWR | O_NOCTTY);
+	if (current_fd < 0) {
+		perror("Could not open /dev/tty0");
+		return false;
+	}
+
+    return true;
+}
+
+static void close_current_terminal(void) {
+    if (current_fd < 0) {
+        return;
+    }
+
+    close(current_fd);
+    current_fd = -1;
+}
+
+static int get_active_terminal(void) {
+    struct vt_stat stat;
+    if (ioctl(current_fd, VT_GETSTATE, &stat) != 0) {
+        perror("Could not retrieve current termimal state");
+        return -1;
+    }
+    return stat.v_active;
+}
+
+static bool get_terminal_size(int fd, struct winsize *size) {
+	if (ioctl(fd, TIOCGWINSZ, size) != 0) {
+        int errsv = errno;
+        perror("Could not retrieve current terminal size");
+        errno = errsv;
+        return false;
+	}
+    return true;
+}
+
+static bool set_terminal_size(int fd, struct winsize *size) {
+    if (ioctl(fd, TIOCSWINSZ, size) != 0) {
+        int errsv = errno;
+        perror("Could not update current terminal size");
+        errno = errsv;
+        return false;
+    }
+    return true;
+}
+
+static bool shrink_terminal(int fd) {
+    struct winsize size = { 0, 0, 0, 0 };
+    
+    if (!reset_terminal(fd, &size)) {
+        perror("Could not shrink terminal size");
+        return false;
+    }
+
+    size.ws_row = floor((float)size.ws_row * height_factor);
+    if (!set_terminal_size(fd, &size)) {
+        perror("Could not shrink terminal size");
+        return false;
+    }
+
+    return true;
+}
+
+static bool reset_terminal(int fd, struct winsize *size) {
+    if (!get_terminal_size(fd, size)) {
+        perror("Could not reset terminal size");
+        return false;
+    }
+
+    /* Test-resize by two rows. If the terminal is already maximised, this will fail and we can exit early. */
+    size->ws_row += 2;
+    if (!set_terminal_size(fd, size)) {
+        bool is_max = (errno == EINVAL);
+        size->ws_row -= 2;
+        return is_max;
+    }
+
+    size->ws_row = floor((float)size->ws_row / height_factor);
+    if (!set_terminal_size(fd, size)) {
+        if (errno != EINVAL) {
+            perror("Could not reset terminal size");
+            return false;
+        }
+
+        /* Size too large. Reduce by one row until it fits. */
+        do {
+            size->ws_row -= 1;
+        } while (size->ws_row > 0 && !set_terminal_size(fd, size) && errno == EINVAL);
+
+        if (errno != EINVAL || size->ws_row == 0) {
+            perror("Could not reset terminal size");
+            return false;
+        }
+    } else {
+        /* Size fits but may not max out available space. Increase by one row until it doesn't fit anymore. */
+        do {
+            size->ws_row += 1;
+        } while (set_terminal_size(fd, size));
+
+        if (errno != EINVAL) {
+            perror("Could not reset terminal size");
+            return false;
+        }
+
+        size->ws_row -= 1;
+    }
+
+    return true;
+}
+
+
+/**
+ * Public functions
+ */
+
+bool bb_terminal_init(float factor) {
+    if (!reopen_current_terminal()) {
+        perror("Could not prepare for terminal resizing");
+        return false;
+    }
+
+    current_vt = get_active_terminal();
+    if (current_vt < 0) {
+        perror("Could not prepare for terminal resizing");
+        return false;
+    }
+
+    height_factor = factor;
+    return true;
+}
+
+void bb_terminal_shrink_current(void) {
+    int active_vt = get_active_terminal();
+    if (active_vt < 0) {
+        perror("Could not resize current terminal");
+        return;
+    }
+
+    if (active_vt < 0 || active_vt > MAX_NR_CONSOLES - 1) {
+        perror("Could not resize current terminal, index is out of bounds");
+        return;
+    }
+
+    if (resized_vts[active_vt - 1]) {
+        return; /* Already resized */
+    }
+
+    if (active_vt != current_vt) {
+        if (!reopen_current_terminal()) {
+            perror("Could not resize current terminal");
+            return;
+        }
+        current_vt = active_vt;
+    }
+
+    if (!shrink_terminal(current_fd)) {
+        perror("Could not resize current terminal");
+        return;
+    }
+
+    resized_vts[current_vt - 1] = true;
+}
+
+void bb_terminal_reset_all(void) {
+    char device[16];
+    struct winsize size = { 0, 0, 0, 0 };
+
+    for (int i = 0; i < MAX_NR_CONSOLES; ++i) {
+        if (!resized_vts[i]) {
+            continue;
+        }
+
+        snprintf(device, 16, "/dev/tty%d", i + 1);
+        int fd = open(device, O_RDWR | O_NOCTTY);
+        if (fd < 0) {
+            perror("Could not reset TTY, unable to open TTY");
+            continue;
+        }
+
+        reset_terminal(fd, &size);
+    }
+}

terminal.h

@@ -0,0 +1,45 @@
+/**
+ * Copyright 2021 Johannes Marbach
+ *
+ * This file is part of buffyboard, hereafter referred to as the program.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+
+#ifndef BB_TERMINAL_H
+#define BB_TERMINAL_H
+
+#include <stdbool.h>
+
+/**
+ * Prepare for resizing terminals by opening the current one.
+ * 
+ * @param factor factor (between 0 and 1) by which to adapt terminal sizes
+ * @return true if the operation was successful, false otherwise. No other bb_terminal_* functions
+ * must be called if false is returned.
+ */
+bool bb_terminal_init(float factor);
+
+/**
+ * Shrink the height of the active terminal by the current factor.
+ */
+void bb_terminal_shrink_current(void);
+
+/**
+ * Re-maximise the height of all previously resized terminals.
+ */
+void bb_terminal_reset_all(void);
+
+#endif /* BB_TERMINAL_H */