On-device screenshot support.

This comes in the form of a command, `screenshot`, which
will read /dev/graphics/fb0 (in a manner very similar to
adb's framebuffer_service) and write to the specified PNG
file.

Additionally, dumpstate now accepts a -p flag (mnemonic:
"picture" or "png") that, when specified, will cause a
screenshot to be captured in the same directory as the
bugreport.

Future work: invoke `dumpstate -p` when the bugreport
keychord is pressed, giving users a convenient way to attach
screenshots to bug reports (or simply take screenshots at
all without developer tools).

Bug: 2216571 (and probably plenty of others)
Change-Id: I36afbc55a0308a7bc01112ef39c4c62777efb203

2 files changed, 134 insertions, 0 deletions

diff --git a/cmds/screenshot/Android.mk b/cmds/screenshot/Android.mk
new file mode 100644
index 0000000..99c7aeb
--- /dev/null
+++ b/cmds/screenshot/Android.mk
@@ -0,0 +1,16 @@
+ifneq ($(TARGET_SIMULATOR),true)
+
+LOCAL_PATH:= $(call my-dir)
+include $(CLEAR_VARS)
+
+LOCAL_SRC_FILES := screenshot.c
+
+LOCAL_MODULE := screenshot
+
+LOCAL_SHARED_LIBRARIES := libcutils libz
+LOCAL_STATIC_LIBRARIES := libpng
+LOCAL_C_INCLUDES += external/zlib
+
+include $(BUILD_EXECUTABLE)
+
+endif
diff --git a/cmds/screenshot/screenshot.c b/cmds/screenshot/screenshot.c
new file mode 100644
index 0000000..46e6507
--- /dev/null
+++ b/cmds/screenshot/screenshot.c
@@ -0,0 +1,118 @@
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+#include <string.h>
+#include <fcntl.h>
+#include <errno.h>
+
+#include <linux/fb.h>
+
+#include <zlib.h>
+#include <libpng/png.h>
+
+#include "private/android_filesystem_config.h"
+
+#define LOG_TAG "screenshot"
+#include <utils/Log.h>
+
+void take_screenshot(FILE *fb_in, FILE *fb_out) {
+    int fb;
+    char imgbuf[0x10000];
+    struct fb_var_screeninfo vinfo;
+    png_structp png;
+    png_infop info;
+    unsigned int r,c,rowlen;
+    unsigned int bytespp,offset;
+
+    fb = fileno(fb_in);
+    if(fb < 0) {
+        LOGE("failed to open framebuffer\n");
+        return;
+    }
+    fb_in = fdopen(fb, "r");
+
+    if(ioctl(fb, FBIOGET_VSCREENINFO, &vinfo) < 0) {
+        LOGE("failed to get framebuffer info\n");
+        return;
+    }
+    fcntl(fb, F_SETFD, FD_CLOEXEC);
+
+    png = png_create_write_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+    if (png == NULL) {
+        LOGE("failed png_create_write_struct\n");
+        fclose(fb_in);
+        return;
+    }
+
+    png_init_io(png, fb_out);
+    info = png_create_info_struct(png);
+    if (info == NULL) {
+        LOGE("failed png_create_info_struct\n");
+        png_destroy_write_struct(&png, NULL);
+        fclose(fb_in);
+        return;
+    }
+    if (setjmp(png_jmpbuf(png))) {
+        LOGE("failed png setjmp\n");
+        png_destroy_write_struct(&png, NULL);
+        fclose(fb_in);
+        return;
+    }
+
+    bytespp = vinfo.bits_per_pixel / 8;
+    png_set_IHDR(png, info,
+        vinfo.xres, vinfo.yres, vinfo.bits_per_pixel / 4, 
+        PNG_COLOR_TYPE_RGB_ALPHA, PNG_INTERLACE_NONE,
+        PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+    png_write_info(png, info);
+
+    rowlen=vinfo.xres * bytespp;
+    if (rowlen > sizeof(imgbuf)) {
+        LOGE("crazy rowlen: %d\n", rowlen);
+        png_destroy_write_struct(&png, NULL);
+        fclose(fb_in);
+        return;
+    }
+
+    offset = vinfo.xoffset * bytespp + vinfo.xres * vinfo.yoffset * bytespp;
+    fseek(fb_in, offset, SEEK_SET);
+
+    for(r=0; r<vinfo.yres; r++) {
+        int len = fread(imgbuf, 1, rowlen, fb_in);
+        if (len <= 0) break;
+        png_write_row(png, (png_bytep)imgbuf);
+    }
+
+    png_write_end(png, info);
+    fclose(fb_in);
+    png_destroy_write_struct(&png, NULL);
+}
+
+int main(int argc, char**argv) {
+    FILE *png = NULL;
+    FILE *fb_in = NULL;
+    if (argc < 2) {
+        fprintf(stderr, "usage: screenshot filename.png\n");
+        exit(1);
+    }
+    fb_in = fopen("/dev/graphics/fb0", "r");
+    if (!fb_in) {
+        fprintf(stderr, "error: could not read framebuffer\n");
+        exit(1);
+    }
+
+    /* switch to non-root user and group */
+    gid_t groups[] = { AID_LOG, AID_SDCARD_RW };
+    setgroups(sizeof(groups)/sizeof(groups[0]), groups);
+    setuid(AID_SHELL);
+
+    png = fopen(argv[1], "w");
+    if (!png) {
+        fprintf(stderr, "error: writing file %s: %s\n", argv[1], strerror(errno));
+        exit(1);
+    }
+
+    take_screenshot(fb_in, png);
+
+    exit(0);
+}